High quality schools CAN close the achievement gap for the poorest minority students

What Works Clearinghouse reviewed this study and found it to meet their evidentiary standards. This was a study of the Promise Academy Middle School in Harlem which provided:

• Extended school day and year with additional after-school tutoring and Saturday classes
• Intensive test preparation including morning, mid-day, after-school, and Saturday sessions
• Student incentives for high achievement, such as money and trips to France
• School health clinic provides students free medical, dental, and mental-health services

Sixth graders were admitted by lottery and showed significant improvements on math and English Language Arts on standardized tests by the 8th grade. The full report is here.
Citation:
Dobbie, W., & Fryer, R. G., Jr., (2009). Are high-quality schools enough to close the achievement gap? Evidence from a social experiment in Harlem. (NBER Working Paper No. 15473). Cambridge, MA: National Bureau of Economic Research.