Two school districts in Tennessee, US, have been hit with a lawsuit for blocking access to websites discussing lesbian, gay, bisexual and trans issues.

The lawsuit was filed by the American Civil Liberties Union (ACLU) on behalf of a school librarian and a number of students.

Last month, ACLU gave school boards in Knox County and Nashville 30 days to unblock the sites. It filed the lawsuit yesterday.

Schools use a web filtering system that censors out unsuitable material such as websites which have sexual content.

The filter also blocks gay educational websites which contain no inappropriate content, such as the Gay and Lesbian Alliance Against Defamation and Marriage Equality USA.

However, it allows access to ‘ex-gay’ sites, which advocate reparative therapy in order to ‘turn’ gay people straight.

The suit stated: “Not only does defendants’ blocking policy discriminate on the basis of content in violation of the First Amendment, the policy further constitutes unlawful viewpoint discrimination.

“Under the defendants’ policy, students may access websites that promote anti-gay views and that advocate that persons should change their sexual orientation through so-called ‘reparative therapy’, but not the web sites of organisations such as the Human Rights Campaign, which is one of the largest civil rights organisations in the United States working to achieve equality under the law for LGBT persons.”

Catherine Crump, the ACLU lead attorney on the case, said: “Allowing access to websites that present one side of an issue while blocking sites that present the other side is illegal viewpoint discrimination.

“This discriminatory censorship does nothing to make students safe from material that may actually be harmful, but only hurts them by making it impossible to access important educational material.”

“While schools may have an interest in using filters to block material that could be harmful to minors, blocking access to information about LGBT issues while allowing anti-gay information is unlawful and potentially dangerous,” said Tricia Herzfeld, a staff attorney with the ACLU of Tennessee.

“There is no place for this kind of unconstitutional censorship in our public schools.”

Keila Franks, a 17-year-old student at Hume-Fogg High School in Nashville and a plaintiff on the case, said: “Students need to be able to access information about their legal rights or what to do if they’re being harassed at school.

“It’s completely unfair for schools to keep students in the dark about such important issues and treat websites that just offer information like they’re something dirty.”