CHICAGO (CBS) — The American Civil Liberties Union recently put out a letter complaining that a North Shore school district was using software that blocked gay and lesbian-oriented Web sites, leaving the school district “furious.”

Gay Chicago Magazine reports Avoca School District 37 in Wilmette never says the ACLU never called its officials to point out the problem before complaining about it.

On Thursday of last week, the ACLU issued a letter of complaint addressed to School District Supt. Joe Porto. The letter said the filtering software the district is using, provided by Lightspeed Systems, “improperly censor(s) Web sites advocating the fair treatment of lesbian, gay, bisexual, and transgender persons.”

The software allows administrators to block several categories based on various criteria. The letter says GLBT Web sites are blocked under the category of “education.lifestyles,”

These Web sites include those for the Gay-Straight Alliance Network, Day of Silence, and other Web sites the ACLU says could benefit students, the letter said.

The filter does not block Web sites with proclamations against homosexuality, such as the Illinois Family Institute, the letter pointed out.

The ACLU said the blocking software violates the students’ First Amendment rights.

But Porto told Gay Chicago Magazine the school district staff did not know they were blocking those sites when they set up the software. He told the magazine there are “boxes you check or don’t check,” and the district followed what other districts have done.

Porto told the magazine the ACLU made it look as if the district had deliberately blocked software that would help gay and lesbian students by raising the issue in a news release without contacting the district first.

He told the magazine there is “a long history in this area of being tolerant and very sensitive to those issues.”

Software to block inappropriate Web sites for students is required by law, Porto told the magazine.