Explaining Charter School Effectiveness
利用马萨诸塞州特许学校的大样本数据，研究发现城市特许学校能显著提升学生成绩，尤其对非白人和低起点学生效果明显，而非城市特许学校普遍无效，且效果差异与学校特色如教学时长和理念相关。
Estimates using admissions lotteries suggest that urban charter schools boost student achievement, while charter schools in other settings do not. We explore student-level and school-level explanations for these differences using a large sample of Massachusetts charter schools. Our results show that urban charter schools boost achievement well beyond ambient non-charter levels (that is, the average achievement level for urban non-charter students), and beyond non-urban achievement in math. Student demographics explain some of these gains since urban charters are most effective for non-whites and low-baseline achievers. At the same time, non-urban charter schools are uniformly ineffective. Our estimates also reveal important school-level heterogeneity in the urban charter sample. A non-lottery analysis suggests that urban schools with binding, well-documented admissions lotteries generate larger score gains than under-subscribed urban charter schools with poor lottery records. We link the magnitude of charter impacts to distinctive pedagogical features of urban charters such as the length of the school day and school philosophy. The relative effectiveness of urban lottery-sample charters is accounted for by over-subscribed urban schools' embrace of the No Excuses approach to education.