The group had previously issued a statement saying the “allegations” that it had distributed a booklet containing graphic depictions of sex acts “are simply lies.”
However, the group on Friday said it had mistakenly offered the guide, titled “Little Black Book: Queer in the 21st Century,” at the April 30 event.
A representative from the AIDS Action Committee, which publishes the manual, called it a “very targeted publication for gay men over 18.”
Among the items at issue in the booklet are a description of fisting and photographic instructions on the correct use of condoms.
The guide also contained a list of clubs “for the discerning queer boy.”
The father of one six-year-old boy who came home with the booklet was arrested after protesting at the group’s headquarters.
GLSEN has apologized for the error and promised to redouble efforts to screen materials in the future.