On average, attending an SSC increased on-time high school graduation rates for the four student cohorts in the present analysis by 9.4 percentage points, an effect that is equivalent in magnitude to roughly 44 percent of the gap in graduation rates between white students and students of color in New York City during the same period. For these student cohorts, attending an SSC also increased the probability of
graduating from high school in four years and attending a postsecondary education program the following year by 8.4 percentage points. It is rare to find such large positive effects for a rigorously evaluated large-scale education reform and rarer still to see such effects continue into college. Hence, the present findings are unusually promising.
Remarkably, SSCs achieve these gains for enrollees at a lower average total cost per graduate than that for their control group counterparts — roughly 14 percent to 16 percent lower. Interestingly, both SSC enrollees and control group enrollees attend high schools that turn out to have per-pupil costs somewhat higher than those of the average New York City high school and substantially higher than those of the largest high schools, which have significant economies of scale. Yet the per-pupil costs for the specific high schools that SSC enrollees and their control group counterparts attended are roughly similar. And, because more SSC students successfully graduate and fewer require an expensive fifth year of high school, the cost per graduate is significantly lower for SSC students than for their control group counterparts. These findings are consistent regardless of the approach used to estimate teacher costs, student composition, facility usage, start-up costs, or partner contributions to the schools.
Still, there is more work to be done. Roughly 30 percent of target SSC enrollees do not graduate from high school on time and, even among those who do, roughly 31 percent do not go on to postsecondary education. In addition, the very small postsecondary effects reported for students who enter high school performing far below grade level suggest that additional investment will be required to help these students obtain the skills they need to make at least some form of postsecondary education a viable option, a transition that will become increasingly important in the twenty-first-century labor market.
In summary, the present findings provide strong evidence that a large-scale high school reform for youths who are far along in the K-12 pipeline, many of whom are academically below grade level when they enter high school, can have sizable positive effects on high school graduation, attainment of a Regents diploma, and postsecondary enrollment.
Still the debate remains as other cities who tried this approach rather had mixed results. Also some researchers have questions with the methodology being used:
Some researchers questioned whether the findings should be seen as a definitive endorsement of small schools in general. Because the research examined only small schools that had more applicants than seats — by definition, the popular small schools — the lowest-performing small schools may not have been included at all.
The study also didn’t look at all of the small schools opened during the Bloomberg administration. An additional 93 small schools opened from 2002 to 2008, but were left out because they were either academically selective, transfer schools, or combined middle and high schools. (source)