More than 3 million students now attend public charter schools, according to a new report from the National Alliance for Public Charter Schools. That’s the most in the country’s history. In the last school year, enrollment in charter schools grew by more than 200,000 students.

There are more than 6,900 charter schools in the country, including 300 new ones that opened in fall 2016. Over the past decade, nationwide enrollment has almost tripled, up from 1.2 million students in the 2006-2007 school year.