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Background: Fewer than 1/4th of US children and adolescents meet physical activity (PA) guidelines, leading to health disparities that track into adulthood. Neighborhood opportunity may serve as a critical modifiable factor to improve fitness attainment and reduce these disparities. We drew data from the Child Opportunity Index to examine associations between neighborhood indicators of opportunity for PA and multiple fitness indicators among New York City public school youth. Methods: Multilevel generalized linear mixed models were used to estimate the overall and sex-stratified associations between neighborhood indicators (green space, healthy food, walkability, commute time) and indicators for physical fitness [curl-ups, push-ups, Progressive Aerobic Cardiovascular Endurance Run (PACER), sit-and-reach] using the New York City FITNESSGRAM data set. Results: The analytic sample [ n  = 299,839; median (interquartile range) age = 16 (12-17)] was 50.1% female, 37.5% Hispanic, 26.2% non-Hispanic Black, and most (69.5%) qualified for free/reduced price school meals. Neighborhood indicators were positively associated with higher values of indicators for physical fitness. The strongest associations were observed between walkability and both BMI and PACER, and commute time with BMI, push-ups, and PACER. For example, walkability had the greatest magnitude of effects for BMI and muscular strength and endurance (BMI: β : -0.75, 95% confidence interval, CI: -1.01 to -0.49; PACER: β : 1.98, 95% CI: 1.59 to 2.37), and particularly for girls compared with boys (BMI, girls: β : -0.91, 95% CI: -1.22 to -0.66); BMI, boys: β : -0.56, 95% CI: -0.86 to -0.25); PACER, girls: β : 2.11, 95% CI: 1.68 to 2.54; push-ups, boys: β : 1.71, 95% CI: 1.31 to 2.12). Conclusion: Neighborhood indicators were associated with multiple measures of youth fitness. Continued research on neighborhood opportunity and youth fitness may better inform place-based public health interventions to reduce disparities.

Recent national trends in the United States indicate a significant increase in childhood obesity, a major public health concern with documented physical and mental comorbidities and sociodemographic disparities. We aimed to estimate the prevalence of obesity and severe obesity among youth in New York City (NYC) before the COVID-19 pandemic and examine time trends overall and by key characteristics. We included all valid height and weight measurements of kindergarten through 8th grade public school students aged 5 to 15 from school years 2011-12 through 2019-20 (N = 1,370,890 unique students; 5,254,058 observations). Obesity and severe obesity were determined using age- and sex-specific body mass index percentiles based on the Centers for Disease Control and Prevention growth charts. Analyses were performed using multivariate logistic regression models with repeated cross-sectional observations weighted to represent the student population for each year and clustered by student and school. Among youth attending public elementary and middle schools in NYC, we estimate that 20.9% and 6.4% had obesity and severe obesity, respectively, in 2019-20. While consistent declines in prevalence were observed overall from 2011-12 to 2019-20 (2.8% relative decrease in obesity and 0.2% in severe obesity, p<0.001), increasing trends were observed among Black, Hispanic, and foreign-born students, suggesting widening disparities. Extending previous work reporting prevalence estimates in this population, nearly all groups experienced significant increases in obesity and severe obesity from 2016-17 to 2019-20 (relative change = 3.5% and 6.7%, respectively, overall; p<0.001). Yet, some of the largest increases in obesity were observed among those already bearing the greatest burden, such as Black and Hispanic students and youth living in poverty. These findings highlight the need for greater implementation of equity-centered obesity prevention efforts. Future research should consider the influence of the COVID-19 pandemic and changes in clinical guidance on childhood obesity and severe obesity in NYC., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Purpose: This paper aims to examine the association between asthma severity and one-year lagged fitness in New York City Public school youth by neighborhood opportunity., Methods: Using the Child Opportunity Index 2.0 and individual-level repeated measures NYC Office of School Health (OSH) fitness surveillance data (2010-2018), we ran multilevel mixed models stratified by neighborhood opportunity, adjusting for sex, race/ethnicity, grade level, poverty status, and time. Asthma severity was based on a physician-completed Asthma Medication Administration Form (MAF) from each school year and drawn from the Automated Student Health Record (ASHR)., Results: Across all youth in grades 4-12 (n = 939,598; 51.7 % male; 29.9 % non-Hispanic Black, 39.3 % Hispanic; 70.0 % high poverty), lower neighborhood opportunity was associated with lower subsequent fitness. Youth with severe asthma and very low and low neighborhood opportunity had the lowest 1-year lagged fitness z-scores - 0.24 (95 % CI, -0.34 to -0.14) and - 0.26 (95 % CI, -0.32 to -0.20), respectively, relative to youth with no asthma and very high opportunity., Conclusions: An inverse longitudinal relationship between asthma severity and subsequent fitness was observed. Study findings have implications for public health practitioners to promote physical activity and improved health equity for youth with asthma, taking neighborhood factors into account., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Inc.)

Neighborhood environments can support fitness-promoting behavior, yet little is known about their influence on youth physical fitness outcomes over time. We examined longitudinal associations between neighborhood opportunity and youth physical fitness among New York City (NYC) public school youth. The Child Opportunity Index (COI), a composite index of 29 indicators measuring neighborhood opportunity at the census-tract level, along with scores on 4 selected COI indicators were linked to NYC FITNESSGRAM youth data at baseline. Fitness outcomes (measured annually, 2011-2018) included body mass index, curl-ups, push-ups, and Progressive Aerobic Cardiovascular Endurance Run (PACER) laps. Unstratified and age-stratified, adjusted, 3-level generalized linear mixed models, nested by census tract and time, estimated the association between COI and fitness outcomes. The analytical sample (n = 204,939) lived in very low (41%) or low (30%) opportunity neighborhoods. Unstratified models indicated that overall COI is modestly associated with improved youth physical fitness outcomes. The strongest opportunity-fitness associations were observed for PACER. Stratified models show differences in associations across younger vs. older youth. We find that neighborhood factors are associated with youth fitness outcomes over time, with the strength of the associations dependent on age. Future implications include better informed place-based interventions tailored to specific life stages to promote youth health., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Severe persistent childhood asthma is associated with low physical activity and may be associated with poor physical fitness. Research on the asthma severity-fitness association longitudinally and across sociodemographic subgroups is needed to inform fitness interventions targeting youth with asthma. We evaluated the relationship between asthma severity (categorized as severe, mild, or no asthma) and subsequent fitness in New York City (NYC) public school youth enrolled in grades 4-12 using the NYC Fitnessgram dataset (2010-2018). Longitudinal mixed models with random intercepts were fit to test the association between asthma severity and one-year lagged fitness z-scores by clustering repeated annual observations at the student level. Models were adjusted for sex, race/ethnicity, grade level, poverty status, time, and stratified by sociodemographic factors. The analytic sample included 663,137 students (51% male; 31% non-Hispanic Black, 40% Hispanic; 55% in grades 4-8, 70% high poverty; 87%, 11% and 1% with no, mild, and severe asthma, respectively). Students with severe asthma and mild asthma demonstrated -0.19 (95% CI, -0.20 to -0.17) and - 0.10 (95% CI, -0.11 to -0.10), respectively, lower fitness z-scores in the subsequent year relative to students without asthma. After stratifying by demographics, the magnitude of the asthma severity-fitness relationship was highest for non-Hispanic white vs. all other racial/ethnic subgroups, and was similar across sex, grade level, and household poverty status. Overall, we observed an inverse longitudinal relationship between asthma severity and subsequent fitness among urban youth, particularly non-Hispanic Whites. Future research should examine how neighborhood-level factors impact the asthma severity-fitness relationship across racial/ethnic subgroups., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Child weight status is inversely associated with fitness, but less is known about this relationship across fitness domains. This study examined the longitudinal association between weight status and fitness domains in a large, diverse sample of children. Methods: Data were drawn from the New York City Fitnessgram (2010-2011 to 2017-2018). Height and weight were collected annually and converted to weight status using Centers for Disease Control and Prevention growth charts. Aerobic capacity, muscular strength, and endurance were measured as age and sex standardized z -scores based on the fitness performance tests. Repeated-measures multilevel models were run testing the association between weight status and 1-year lagged fitness domains. Results: The sample included 917,554 children (51.8% male, 39.3% Hispanic, 29.9% non-Hispanic Black, 13.9%, 4.7%, and 1.7% class I, II, and III obesity, respectively). For each fitness domain, fitness scores decreased with increasing weight status across all demographic categories, with the lowest fitness scores observed in children with the most severe obesity, and highest magnitude of effects for aerobic capacity, and particularly among boys, non-Hispanic Whites, and older youth. For example, compared with youth with healthy weight, youth with overweight had 0.28 standard deviation lower aerobic capacity performance [confidence interval (95% CI): -0.29 to -0.28], followed by class 1 obesity ( β  = -0.57, 95% CI: -0.58 to -0.57), class 2 obesity ( β  = -0.88, 95% CI: -0.88 to -0.88), and class 3 obesity ( β  = -1.19, 95% CI: -1.20 to -1.18). Conclusions: Compared with youth with healthy weight, youth at every other weight status had lower subsequent fitness, with the magnitude of the relationship increasing as weight status increased. Future research should examine interventions targeting aerobic capacity to reduce fitness disparities.

NYC FITNESSGRAM, monitored by the New York City (NYC) Department of Education and the NYC Department of Health and Mental Hygiene, functions as the NYC Department of Education's citywide youth fitness surveillance program. Here we present the methods, characteristics, and data used in this surveillance system to monitor physical fitness in public school students (grades kindergarten through 12; initiated in 2006; n = 6,748,265 observations; mean sample of 519,097 observations per year to date) in New York, New York. Youth physical fitness prevalence estimates, longitudinal trends, and spatial analyses may be investigated using continuous fitness composite percentile scores and Cooper Institute for Aerobic Research-defined sex- and age-specific Healthy Fitness Zones. Healthy Fitness Zones are based on individual-child fitness test performance, with standard errors clustered at the school and student levels and adjusted for sociodemographic characteristics. Results may be used to show trends in youth fitness attainment over time and highlight disparities in the fitness prevalence of NYC students. In sum, continuous fitness composite percentile scores offer the opportunity for prospective tracking of shifts in youth physical fitness on a population scale and across subpopulations. NYC FITNESSGRAM can accompany a growing body of surveillance tools demonstrating the potential for population-level surveillance tools to promote global public health., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Obesity is associated with poorer youth fitness. However, little research has examined the magnitude of this relationship in youth with severe obesity. Therefore, we sought to determine the relationship between increasing weight status and fitness within a sample of children and adolescents from New York City public schools., Methods: This study utilized longitudinal data from the NYC Fitnessgram dataset years 2010-2018. Height and weight along with fitness were measured annually during physical education classes. Severity of obesity was defined using body mass index relative to the 95th percentile and then categorized into classes. A composite measure of fitness was calculated based on scores for three fitness tests: aerobic capacity, muscular strength, and muscular endurance. To examine the weight status-fitness relationship, repeated measures mixed models with random-intercepts were constructed. Stratified models examined differences by demographic factors., Results: The sample included 917,554 youth (51.8% male, 39.3% Hispanic, 29.9% non-Hispanic Black, 14.0%, 4.6%, and 1.6% class I, II and III obesity, respectively). Compared to youth with healthy weight, increasing severity of obesity was associated with decreased fitness: overweight (β = - 0.28, 95% CI:-0.29;-0.28), class I obesity (β = - 0.60, 95% CI:-0.60; - 0.60), class II obesity (β = - 0.94, 95% CI:-0.94; - 0.93), and class III obesity (β = - 1.28; 95% CI:-1.28; - 1.27). Stratified models showed the association was stronger among male and non-Hispanic White youth., Conclusion: Findings revealed that more severe obesity was associated with lower fitness. Future research is needed to develop targeted interventions to improve fitness in youth with obesity., (© 2023. The Author(s).)

FITNESSGRAM® is the most widely used criterion-referenced tool to assess/report on student health-related fitness across the US. Potential weight-related biases with the two most common tests of musculoskeletal fitness-the trunk extension and Back-Saver Sit-and-Reach (sit-and-reach)-have been hypothesized, though have not been studied. To determine the association between musculoskeletal fitness test performance and weight status, we use data from 571,133 New York City public school 4th-12th grade students (85% non-White; 75% qualified for free or reduced-price meals) with valid/complete 2017-18 FITNESSGRAM® data. Adjusted logistic mixed effects models with a random effect for school examined the association between weight status and whether a student was in the Healthy Fitness Zone (HFZ; met sex- and age-specific criterion-referenced standards) for the trunk extension and sit-and-reach. Compared to students with normal weight, the odds of being in the HFZ for trunk extension were lower for students with underweight (OR = 0.77; 95% CI: 0.741, 0.795) and higher for students with overweight (OR = 1.10; 95% CI: 1.081, 1.122) and obesity (OR = 1.11; 95% CI: 1.090, 1.13). The odds of being in the HFZ for sit-and-reach were lower for students with underweight OR = 0.85; 95% CI: 0.826, 0.878), overweight (OR = 0.83; 95% CI: 0.819, 0.844) and obesity (OR = 0.65; 95% CI: 0.641, 0.661). Students with overweight and obesity perform better on the trunk extension, yet worse on the sit-and-reach, compared to students with normal weight. Teachers, administrators, and researchers should be aware of the relationship of BMI with student performance in these assessments., Competing Interests: Dr. Andjelka Pavlovic, Ph.D. is the Director of Research and Education in the Division of Youth Education for the Cooper Institute, which is responsible for the FITNESSGRAM®. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Standardized physical fitness monitoring provides a more accurate proxy for youth health when compared with physical activity. Little is known about the utilization of broad-scale individual-level youth physical fitness testing to explore health disparities. We examined longitudinal trends in population-level fitness for 4th-12th grade New York City youth during 2006/7-2016/17 (average n = 510,293 per year). Analyses were performed in 2019. The primary outcome was whether or not youth achieved sex-/age-specific performance levels (called the Healthy Fitness Zone) on the aerobic capacity, muscular strength and muscular endurance tests using the NYC FITNESSGRAM. The Cooper Institute's most recent Healthy Fitness Zone criteria were applied to all tests and years. Prevalence estimates were weighted, accounted for school clustering, adjusted for student-level sociodemographics, and run by sociodemographic subgroups and year. The overall prevalence for meeting 3 Healthy Fitness Zones increased from 15.5% (95%CI: 13.9%-17.0%) in 2006/7 to 23.3% (95%CI: 22.2%-24.4%) in 2016/17 for students in grades 4-12. Fitness for all student groups increased over time, although Hispanic and non-Hispanic black girls consistently had the lowest prevalence of meeting 3 Healthy Fitness Zones as compared to all other race/sex subgroups. Also, 9th-12th graders had a lower prevalence of meeting 3 Healthy Fitness Zones as compared to 4th-8th graders. Given forecasted sharp increases in cardiovascular disease prevalence, routine youth fitness surveillance using standardized, criterion referenced methods can identify important fitness disparities and inform interventions., Competing Interests: The authors have declared that no competing interests exist.

Objective: This study aimed to estimate population-level prevalence of obesity and severe obesity for New York City youth and examine the most recent trends over time., Methods: All public school youth in grades kindergarten through eighth (K-8) (2011-2012 through 2016-2017) with valid weight and height measures were included (N = 1,137,782 unique students; 3,720,297 observations). Age- and sex-specific BMI percentiles for obesity and severe obesity were estimated using Centers for Disease Control and Prevention growth charts. Repeated cross-sectional analyses were conducted using logistic regression, weighting for missing or invalid responses and accounting for clustering by students and schools to examine trends over time and by sociodemographics., Results: Among youth in K-8 (aged 5-15 years, 48.8% girls), the prevalence of obesity and severe obesity in 2011-2012 was 21.5% and 6.4%, respectively, compared with 20.2% and 6.0%, respectively, in 2016-2017. Since 2011-2012, decreasing trends in obesity and severe obesity (relative declines: 6.0% and 6.3%, respectively, P < 0.001) have been observed. Significant decreases were observed for all subgroups (P < 0.001), although there remained disparities in relative declines over time by race/ethnicity and poverty., Conclusions: Decreasing trends in obesity and severe obesity among all New York City K-8 public school youth are promising; however, persistent disparities highlight the need to improve intervention design and implementation strategies for groups disproportionately burdened by obesity., (© 2020 The Obesity Society.)

Recent research demonstrates that youth fitness improvements are associated with lower absenteeism. This study assessed whether the effects of poverty on the longitudinal fitness-absenteeism relationship are consistent across poverty measures at the student, school, and neighborhood levels and across sex in New York City (NYC) public school youth individually followed over 4 years. Negative binomial longitudinal mixed models with random-intercepts were developed stratified by five dichotomized student, school and neighborhood poverty measures and sex to test the change in fitness-lagged absenteeism relationship in six cohorts of NYC middle school students (2006/7-2012/13). Models were adjusted for individual-level race/ethnicity, place of birth, change in obesity status, grade, time, and school size. The sample included 360,743 students (51% male, 39% Hispanic, 28% non-Hispanic black, 69% qualifying for free/reduced price school meals). Adjusted estimates showed an inverse dose-response fitness-absenteeism relationship in high poverty youth across all poverty measures, including the student, school and neighborhood levels. For example, in girls exposed to high poverty based on school neighborhood, absenteeism decreased by 11.3% (IRR = -0.12, 95% CI: -0.20, -0.04), 10.4% (IRR = -0.11, 95% CI: -0.21, -0.02), 6.8% (IRR = -0.07, 95% CI: -0.14, 0.00) and 4.9% (IRR = -0.05, 95% CI: -0.15, 0.04) for students who had a >20% increase, 10-20% increase, <10% change, and 10-20% decrease in fitness from the prior year, respectively, relative to the reference group (>20% decrease in fitness). Future research should explore the impact of tailored interventions for youth that aim to promote youth physical activity at each of the individual, school and neighborhood levels, and particularly among high poverty subgroups., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Extensive research demonstrates the benefits of fitness on children's health and academic performance. Although decreases in health-related fitness may increase school absenteeism, multiple years of prospective, child-level data are needed to examine whether fitness changes predict subsequent chronic absenteeism status., Methods: Six cohorts of New York City public school students were followed from grades 5-8 (2006/2007-2012/2013; N = 349,381). A longitudinal 3-level logistic generalized linear mixed model with random intercepts was used to test the association of individual children's changes in fitness and 1-year lagged chronic absenteeism., Results: The odds of chronic absenteeism increased 27% [odds ratio (OR) 95% confidence interval (CI), 1.25-1.30], 15% (OR 95% CI, 1.13-1.18), 9% (OR 95% CI, 1.07-1.11), and 1% (OR 95% CI, 0.98-1.04), for students who had a >20% decrease, 10%-20% decrease, <10% increase or decrease, and 10%-20% increase in fitness, respectively, compared with >20% fitness increase., Conclusion: These findings contribute important longitudinal evidence to a cross-sectional literature, demonstrating reductions in youth fitness may increase absenteeism. Given only 25% of youth aged 12-15 years achieve the recommended daily 60 minutes or more of moderate to vigorous physical activity, future work should examine the potential for youth fitness interventions to reduce absenteeism and foster positive attitudes toward lifelong physical activity.

Purpose: One-fifth to one-third of students in high poverty, urban school districts do not attend school regularly (missing ≥6 days/year). Fitness is shown to be associated with absenteeism, although this relationship may differ across poverty and gender subgroups., Methods: Six cohorts of New York City public school students were followed up from grades 5 to 8 during 2006/2007-2012/2013 (n = 349,381). Stratified three-level longitudinal generalized linear mixed models were used to test the association between changes in fitness and 1-year lagged child-specific days absent across gender and poverty., Results: In girls attending schools in high/very high poverty areas, greater improvements in fitness the prior year were associated with greater reductions in absenteeism (P = .034). Relative to the reference group (>20% decrease in fitness composite percentile scores from the prior year), girls with a large increase in fitness (>20%) demonstrated 10.3% fewer days absent (incidence rate ratio [IRR] 95% confidence interval [CI]: 0.834, 0.964), followed by those who had a 10%-20% increase in fitness (9.2%; IRR 95% CI: 0.835, 0.987), no change (5.4%; IRR 95% CI: 0.887, 1.007), and a 10%-20% decrease in fitness (3.8%; IRR 95% CI: 0.885, 1.045). In girls attending schools in low/mid poverty areas, fitness and absenteeism also had an inverse relationship, but no clear trend emerged. In boys, fitness and absenteeism had an inverse relationship but was not significant in either poverty group., Conclusions: Fitness improvements may be more important to reducing absenteeism in high/very high poverty girls compared with low/mid poverty girls and both high/very high and low/mid poverty boys. Expanding school-based physical activity programs for youth particularly in high poverty neighborhoods may increase student attendance., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Introduction: Youth health-related fitness positively affects academic outcomes, although limited research has focused on the relationship between fitness and school absenteeism. We examined the longitudinal association between individual children's fitness and lagged school absenteeism over 4 years in urban middle schools., Methods: Six cohorts of New York City public school students were followed from grades 5 through 8 (school years 2006-2007 through 2012-2013; n = 349,381). A 3-level longitudinal generalized linear mixed model was used to test the association of change in fitness composite percentile scores and 1-year lagged child-specific days absent., Results: Adjusted 3-level negative binomial models showed that students with a more than 20% increase, 10% to 20% increase, less than 10% increase or decrease, and 10% to 20% decrease in fitness from the year prior had 11.9% (95% confidence interval [CI], 7.2-16.8), 6.1% (95% CI, 1.0-11.4), 2.6% (95% CI, -1.1 to 6.5), and 0.4% (95% CI, -4.3 to 5.4) lower absenteeism compared with students with a more than 20% fitness decrease., Conclusion: Cumulative effects of fitness improvement could have a significant impact on child absenteeism over time, particularly in high-need subgroups. Future research should examine the potential for school-based fitness interventions to reduce absenteeism rates, particularly for youths who have fitness drop-offs in adolescence.

Purpose: To evaluate whether a change in fitness is associated with academic outcomes in New York City (NYC) middle-school students using longitudinal data and to evaluate whether this relationship is modified by student household poverty., Methods: This was a longitudinal study of 83,111 New York City middle-school students enrolled between 2006-2007 and 2011-2012. Fitness was measured as a composite percentile based on three fitness tests and categorized based on change from the previous year. The effect of the fitness change level on academic outcomes, measured as a composite percentile based on state standardized mathematics and English Language Arts test scores, was estimated using a multilevel growth model. Models were stratified by sex, and additional models were tested stratified by student household poverty., Results: For both girls and boys, a substantial increase in fitness from the previous year resulted in a greater improvement in academic ranking than was seen in the reference group (girls: .36 greater percentile point improvement, 95% confidence interval: .09-.63; boys: .38 greater percentile point improvement, 95% confidence interval: .09-.66). A substantial decrease in fitness was associated with a decrease in academics in both boys and girls. Effects of fitness on academics were stronger in high-poverty boys and girls than in low-poverty boys and girls., Conclusions: Academic rankings improved for boys and girls who increased their fitness level by >20 percentile points compared to other students. Opportunities for increased physical fitness may be important to support academic performance., (Copyright © 2014 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.)

Introduction: Although studies have shown that childhood obesity overall is on the decline among New York City (NYC) public school children, the prevalence of severe childhood obesity has not been studied., Methods: We used height and weight measurements of 947,765 NYC public school students aged 5 to 14 years in kindergarten through 8th grade (K-8), from school years 2006-07 through 2010-11. We used age- and sex-specific body mass index (BMI) percentiles according to Centers for Disease Control and Prevention growth charts to define childhood obesity (BMI ≥ 95th percentile) and severe childhood obesity (BMI ≥120% of 95th percentile) and to identify biologically implausible values (BIV). Multivariable logistic models tested for trends in obesity and severe obesity prevalence. To evaluate misclassification, we recalculated prevalence estimates for the most recent school year (2010-11) including the student records identified as BIV who were also declared severely obese (BMI ≥ 120% of 95th percentile). We refer to this subgroup of BIVs as "high BIV.", Results: Severe obesity among NYC public school students in grades K-8 decreased 9.5% from the 2006-07 school year (6.3%) to the 2010-11 school year (5.7%), and obesity decreased 5.5% (from 21.9% to 20.7%). The prevalence of severe obesity and obesity was highest among minority, poor, and male children. Severe obesity declined in prevalence among every subgroup, with the greatest effect among white students and wealthy students. Severe obesity prevalence increased with age, and obesity prevalence peaked among those aged 7 to 10 years. For the 2010-11 school year, including high BIVs increased severe obesity prevalence from 5.7% to 6.6% and increased obesity prevalence from 20.7% to 21.5%., Conclusion: Among all subgroups of NYC public school children in grades K-8, the reduction in severe obesity was greater than the reduction in overall obesity. Efforts to decrease obesity in NYC have affected the severely obese; however, monitoring of this specific subgroup should continue because of differences in trends and greater health risks.