One of the most wide-ranging reforms in pub­lic edu­ca­tion in the last decade has been the reor­ga­ni­za­tion of large com­pre­hen­sive high schools into small schools with roughly 100 stu­dents per grade. SEII researcher used assign­ment lot­ter­ies embed­ded in New York City’s high school match to esti­mate the effects of atten­dance at a new small high school on stu­dent achievement. More than 150 uns­e­lec­tive small high schools cre­ated between 2002 and 2008 have enhanced auton­omy, but oper­ate within-district with tra­di­tional pub­lic school teach­ers, prin­ci­pals, and collectively-bargained work rules. Esti­mates show pos­i­tive score gains in Mathematics, English, Science, and History, more credit accu­mu­la­tion, and higher grad­u­a­tion rates. Small school atten­dance causes a sub­stan­tial increase in col­lege enroll­ment. Stu­dents at small schools are more engaged and closely mon­i­tored, despite fewer course offer­ings and activ­i­ties. Teachers report greater feed­back, increased safety, and improved collaboration.

http://seii.mit.edu/research/study/small-high-schools-and-student-achievement-lottery-based-evidence-from-new-york-city/