Purpose: We aim to better understand the curricular, staffing, and achievement trade-offs entailed by expansions of high-school computer science (CS) for students, schools, and school leaders. Methods: We use descriptive, correlational, and quasi-experimental methods to analyze statewide longitudinal course-, school-, and staff-level data from California, where CS course taking has expanded rapidly. Findings: We find that these rapid CS course expansions have not come at the expense of CS teachers' observable qualifications (namely certification, education, or experience). Within-school course taking patterns over time suggest that CS enrollment growth has come at the expense of social studies, English/language arts (ELA), and arts courses, as well as from other miscellaneous electives. However, we find no evidence that increased enrollment of students in CS courses at a school has a significant effect on students' math or ELA test scores. Implications: Flexible authorization requirements for CS teachers appear to have allowed school leaders to staff new CS courses with teachers whose observable qualifications are strong, though we do not observe teachers' CS teaching skill. Increasing CS participation is unlikely to noticeably improve school-level student test scores, but administrators also do not need to be overly concerned that test scores will suffer. However, school leaders and policymakers should think carefully about what courses new CS courses will replace and whether such replacements are worthwhile. [ABSTRACT FROM AUTHOR]