Participation is the objective of federal Title IX and other rules that have opened innumerable opportunities for girls and women in academics and sports.

Now, a growing movement in Pennsylvania threatens to turn that idea on its head by limiting girls' participation through a side door in the legal framework for high school girls' sports.

Only one in 27 girls competed in high school sports when Title IX was adopted in 1972; now two in five are on high school teams.

In 1975 the Commonwealth Court rejected a Pennsylvania Interscholastic Athletic Association rule that had barred girls from practicing or competing against boys. Then, such competition often was the only means for girls to even attempt to compete in interscholastic sports, and the state's equal rights law, also passed in 1972, forbade gender-based discrimination.

Now, many boys play on girls' high school teams if the same sport is not offered to boys, which is a bad idea on several scores. First, it diminishes participation by girls, contradicting the fundamental purpose of Title IX. And it's dangerous. Beyond sexual differences, there are fundamental differences in speed, strength and aggression between, say, an average 15-year-old freshman girl and an average 18-year-old senior boy. Allowing them to play against one another, especially in a contact sport like field hockey, invites injury.

The PIAA sent a survey to 1,470 member schools, asking about boys on girls' teams. Only 742 responded. Of those, 38 reported boys playing field hockey, 14 had boys playing girls volleyball, eight playing girls lacrosse, five playing girls soccer and one each in swimming and tennis.

Attorney General Kathleen Kane has erred in defending the law against the PIAA's effort to overturn it in favor of girls' participation and safety. The Legislature should amend the law if the Commonwealth Court rejects the PIAA effort.