D.C.’s charter schools aren’t only growing faster than traditional public schools, but they’re also showing bigger improvements in citywide standardized tests.

A new report from the D.C. Fiscal Policy Institute out today found that proficiency in math and reading—as measured by the annual D.C. Comprehensive Assessment System—generally increased at the city’s charter schools, while falling at public schools. According to the report, the median proficiency level at the 43 charter schools studied rose from 44.2 to 50.2 percent from 2008 to 2012, while it fell from 40.4 to 36.7 percent at the 109 public schools.

When averaged out, proficiency across the entire public school system—which includes public schools and public charter schools—fell by 0.6 percent, mostly due to a 6.5 percent decline in reading proficiency. Worse yet, though, is the geographic distribution of declining proficiency rates: schools in wards 4, 5, 7, and 8 saw declines of between two and six percent, while schools in wards 1, 2, 3, and 6 generally saw improvements.

So what does this mean for the city’s public education sector, which has promised dramatic proficiency increases at the lowest-performing schools by 2017? According to the group, D.C. has to dedicate more resources to struggling schools, and those resources have to focus on more than just improving instruction.

“As D.C. leaders look to policy solutions to improve student achievement, it is critical to acknowledge the role of key non-instructional services that can help these children be better prepared to participate in school. This could mean greater investment in mental health services, out-of-school time programs, and parent engagement efforts in public schools, to name a few,” said the report.

Charter school advocates have long argued that charter schools do better because they’re able to be more flexible; they don’t have a teachers contract to contend with, and can adjust instruction and programming more quickly than traditional public schools. Still, critics say that charter schools also expel students at much higher rates, leaving D.C. public schools with little choice but to take some of the toughest students. Most education experts say that D.C. boasts good and bad schools of both types; charter schools aren’t always better than their public school counterparts, for one.

Last December another D.C. organization found that test scores for third-graders in both public and charter schools hadn’t increased appreciably over the last few years, though it did say that the city’s investment in early education could pay big dividends in the future.

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