The impact study capitalizes on random elements of the NYCDOE's centralized high school admissions process. Each lottery for a small school of choice is a naturally occurring experiment, which, after some adjustments, makes it possible to produce valid estimates of the effects of enrollment in SSCs on student academic outcomes. The impact study follows four cohorts of students--those entering high school in the fall of 2005, 2006, 2007, and 2008. The primary sources of data for the analyses are High School Application Processing System (HSAPS) data and school records, which were obtained from the NYCDOE.
Because about 7% of SSC lottery winners do not enroll in an SSC and about 35% of those who lose a particular SSC lottery enroll in a different SSC (whether through HSAPS assignment or otherwise), the contrast between the two groups is diluted. Therefore the estimated effects of winning an SSC lottery are converted into the estimated effects of enrolling in an SSC by means of instrumental variables analysis. For details, see Howard Bloom, Saskia Levy Thompson, and Rebecca Unterman, "Transforming the High School Experience: How New York City’s New Small Schools Are Boosting Student Achievement and Graduation Rates" (New York: MDRC, 2010), at http://www.mdrc.org/publication/transforming-high-school-experience.
The MDRC school characteristics study uses extant data from the U.S. Department of Education, New York State Report Card, and NYCDOE, along with aggregate HSAPS and student records data in a school-level database, to analyze changes in high school options and student enrollment over time. The analyses identify patterns and trends among schools for a number of instruction-related, demographic, and performance-based characteristics by school type as defined by size and selectivity.