California Gov. Gavin Newsom signed a new bill into law last week that imposes new regulations on charter schools and increases school districts’ power to stop new charters from opening. Too bad Newsom and other critics didn’t bother reading The Fordham Institute’s new study, which finds having more charter schools benefit minority students the most—even if they’re enrolled in district public schools.

Unlike previous studies comparing charter and district public-school student achievement, the Fordham study examines the academic performance of students within communities based on charter-school market share. Specifically, study author David Griffith focused on the percentages of students enrolled in charter schools and the average achievement of all students within a geographic school district, including students in district public schools. The results are impressive.

For both black and Hispanic students, as the charter-school share increases over time, so does English language arts (ELA) and math achievement for all students in those groups—both charter and district public-school students.

In smaller urban areas, a higher charter-school share growing from 0 percent to 50 percent is associated with black student ELA and math achievement gains of 0.3 and 0.4 grade levels, respectively. Likewise, associated Hispanic student achievement gains amount to 0.3 grade levels in math, although no associated gains were found in ELA.

Student achievement gains are even greater in larger urban areas—which is significant since these districts enroll the most black and Hispanic students.

Based on 21 school districts with at least 2,500 black students enrolled in each grade, a higher charter-school share growing from 0 percent to 50 percent is associated with black student ELA and math achievement gains of 0.8 and 0.7 grade levels, respectively.

Similarly, based on 27 urban districts enrolling at least 2,500 Hispanic students in each grade, a higher charter-school market share growing from 0 percent to 35 percent is associated with ELA and math achievement gains of 0.7 grade levels each.

As Griffith sums up:

In light of this evidence and the innumerable other studies that suggest enrolling in a charter is associated with substantial achievement gains for black and Hispanic students, it is simply wrong to stand in the way of charters’ continued growth in these communities if closing racial achievement gaps is truly the goal. Henceforth, the burden of proof falls on those who would claim otherwise.