You’re a Virginia public school system. Say, Prince William County. You want to protect the kids from the vile creatures of the Internet. You install filtering software to keep out the bad stuff. It’s the law in the Old Dominion, actually.

But if you’re a gay student in, say, Prince William County, you don’t have access to some websites which are neither vile nor pornographic. So the ACLU on Monday sent a letter to Prince William schools, demanding that they remove their filter for gay-lesbian-bisexual and transgender websites immediately.

It’s not an easy question. But the ACLU says that the filtering system Prince William uses, called Blue Coat, allows intolerant anti-gay sites through, but not positive or helpful ones. Here’s the ACLU’s video explaining the situation, and both sides weigh in after the jump.

Blue Coat, based in Sunnyvale, Calif., provides filtering software to many school districts, general counsel Betsy Bayha said, and they’ve had this discussion with the ACLU before. Still, it’s up to the individual systems to filter out what they do and don’t want to get through.

The ACLU recognizes the need to screen out the heavy-duty adult stuff, their Virginia executive director Kent Willis said Tuesday. “But if you’re going to allow the Key Club and many other organizations to access the Internet, then you have to allow the gay and lesbian clubs to do so too.”

The ACLU’s letter to Prince William says their system blocks out sites such as the Gay Lesbian and Straight Education Network, Day of Silence and It Gets Better, which provide support and resources for homosexual students. But it allows access to sites such as People Can Change, Exodus International and Parents and Friends of Ex-Gays, which all advocate for changing from gay to straight.

Prince William schools spokesman Ken Blackstone said the district was looking at the ACLU’s letter, “we’ll be thoroughly reviewing it and we’ll respond to them.” He noted that both the federal Children’s Internet Protection Act and Virginia code impose specific requirements for filtering Internet access.

But perhaps most tricky: Prince William can only use one set of filters for its entire system of 80,000 students, from pre-kindergarten through 12th grade, Blackstone says. So what goes at Marumsco Hills Elementary School also goes at Osbourn Park High School.

Prince William was given two weeks to respond to the ACLU’s letter, which was also sent to districts in Michigan, Pennsylvania and Texas who also use Blue Coat.