The American Civil Liberties Union filed a lawsuit Monday against a Missouri school district as part a national campaign aimed at stopping schools’ internet filtering software from blocking access to educational websites about gay, lesbian, and transgender issues.

The civil rights organization said in a news release that the lawsuit was filed in federal court in Jefferson City, Mo., against the Camdenton R-III School District in central Missouri on behalf of organizations whose websites are blocked by the filter. Those organizations include the Matthew Shepard Foundation, and Parents, Families and Friends of Lesbians and Gays National, a Washington, D.C.-based advocacy group.