The objective of this study was to determine the effectiveness of a district-wide professional development effort based on a modified Ramp-Up Program, designed to help high school teachers improve the reading skills of their students. Ramp-Up is a two-year course that seeks to accelerate the learning progress of entering high school students who are two or more years behind grade level in English/Language Arts. The course assumes that students can decode text and are reading at least at a Grade 3 level. Activities focus on helping students make rapid progress toward becoming fluent readers, develop wider vocabularies, and comprehend grade level texts through a variety of instructional approaches: (a) Independent Reading (Allington, 2001; Beers, 2003); (b) Read-Aloud/Think-Aloud/ Talk-Aloud (Hahn, 2002; Richardson, 2000); (c) whole-group and small-group reading and writing instruction (Fountas & Pinnell, 1996; Pearson, 1994); and, (d) collaborative learning situations including cross-age tutoring and service learning (Labbo & Teale, 1990). Pilot testing showed that the course had a positive effect on high school students' scores on norm-referenced reading and language arts tests (Muñoz, 2007). In this study, the effectiveness of this professional development model was evaluated using the five levels outlined by Guskey (2000; 2001a; 2001b) for evaluating professional development activities in education. The first level assessed participants' reactions, while the second level assessed participants' learning through pre- and post-measures of knowledge and skills specific to the program. The third level assessed participants' perceptions of organizational support to enable change, and the fourth level focused on participants' use of new knowledge and skills at the classroom level. The fifth and final level assessed the impact on student learning outcomes using results from statewide accountability assessments in reading. [ABSTRACT FROM AUTHOR]