Wall Street Journal:

The paper’s authors, three professors of economics or education policy, explain what happened after Massachusetts raised its charter cap in 2010. The state set rules encouraging successful charter schools—deemed “proven providers”—to seed new campuses. Most follow a “no excuses” framework, with high expectations and a low tolerance for misbehavior.

After the cap was lifted, growth came rapidly. By 2015 the share of Boston’s sixth-graders attending a charter school had risen from 15% to 31%. Yet applications increased even faster, to the point that there were two hopefuls for each open seat. Oversubscribed charters award admission by lottery, which randomizes the results. “Comparing the outcomes of students who receive lottery offers to those that do not,” the authors write, shows “large positive impacts of charter attendance on test scores.”

Notably, the charter spinoffs were equally successful “while enrolling students that appear more representative of the general Boston population.” Compared with peers at Boston Public Schools, these pupils had lower previous test scores, were more likely to qualify for subsidized lunch and had similar rates of special needs and limited English.