During summer vacation, many students lose knowledge and skills. By the end of summer, students perform, on average, one month behind where they left off in the spring. Participation in summer learning programs should mitigate learning loss and could even produce achievement gains. Indeed, educators and policymakers increasingly promote summer…

Tennessee's Project STAR (Student Teacher Achievement Ratio) randomly assigned 7,000 K-3 students to small classes (13-17 pupils), regular classes (22-26 pupils), and regular-with-aide classes. Small classes ameliorate large schools' effects, reduce grade retention and discipline problems, benefit minority students substantially, allow students…