Three transgender seniors at a Pennsylvania high school are suing the school district over a new policy that requires students to use restrooms corresponding to their biological sex.

The Pine-Richland School District previously allowed transgender students to use restrooms corresponding to their "gender identity." But the school board last month passed a resolution that students must use restrooms that "correspond to their biological sex" or use unisex facilities.

Two 18-year-old plaintiffs were born biologically male but identify as female; one 17-year-old was born biologically female and identifies as male. They say they are being discriminated against by the new policy, which their federal lawsuit filed Thursday seeks to reverse.

Judges in North Carolina and Wisconsin have agreed such policies violate federal law.

The district declined to comment on the lawsuit.