Still, critics argue that the law has come with unintended consequences. Some advocacy groups, including the American Sports Council, say the law disadvantages male athletes. Meanwhile, as the writers Linda Flanagan and Susan Greenberg have reported, others are concerned that the shifts brought on by Title IX are coming “at a serious cost for many female athletes” because they’ve increased the health risks for players and prompted a drop in the number of women coaches, among other ramifications.

Flanagan and Greenberg did acknowledge the progress that has been made thanks to the law, however: “Title IX has clearly triumphed in its mission to equalize the playing field for young women. Its impact can be felt at every level of competition,” they wrote. “The numbers bear it out.”

But do they really? Nearly 4,500 public high-schools across the United States have large gender inequality in sports and could be in violation of Title IX, according to a new National Women’s Law Center analysis of 2011-12 Department of Education data. These campuses account for well over a fourth—28 percent—of the country’s public high schools. Some states have far more inequality than others, though most of them have large gaps in at least one in five high schools. In six of those states, large gaps exist in more than half of all public schools.

The state where gender inequality in sports is most severe? Georgia, where two-thirds of high schools have large gaps. In fact, each of the 10 worst-ranking states—including Alabama, Mississippi, and Tennessee—are in the South.

A gap is considered “large” if the difference between the percentage of spots on teams allocated to girls and that allocated to boys is 10 points or higher. If girls account for, say, 55 percent of the population at a school but only get 43 percent of all the spots on teams, that school has a 12 percent gap. That’s similar to the formula used by the federal government in enforcing Title IX, which says that a school can demonstrate compliance by showing the percentage of spots for girls and that for boys are about the same. (States where the gaps are smallest include Vermont, Hawaii, Maine, and Maryland.)

“This data shows what schools are very likely to be out of compliance” with Title IX, said Neena Chaudhry, the senior counsel at the National Women’s Law Center.

Whether that’s going to change, however, is an open question. According to Chaudhry, although it does conduct investigations and regulate the law, the federal government has never taken funding away from an institution because of noncompliance with Title IX.

It’s true that it’s hard to assess whether a school is denying girls of sports participation or simply isn’t providing an athletic opportunity because girls aren’t interested in participating. Schools must proactively prove that the latter is the case to demonstrate Title IX compliance by surveying female students and coaches to gauge their athletic interests and ensure they’re “satisfying girls’ interests,” Chaudhry said. But Chaudhry, who also directs the law center’s Equal Opportunities in Athletics program, says she’s never heard of a school with a large gender gap successfully proving that it’s indeed fulfilling their interests. Typically the school just hasn’t done its due diligence.