MONTGOMERY, AL – In 2001, the Southern Poverty Law Center (SPLC) created “Mix It Up at Lunch Day,” an annual event to encourage schoolchildren to spend time with another kid with whom they might not normally associate.

The Montgomery-based nonprofit civil rights organization—best known for its court victories against white supremacist groups, and its monitoring of extremist organizations—designed the project as a way for schools to promote tolerance, with a long-term goal of breaking up cliques and sensitizing kids to the evils of bullying. More than 2,500 schools take part nationwide, most of them on Oct. 30.

This month, the conservative American Family Association (AFA) sent an email to its supporters, in which it denounced the event as “a nationwide push to promote the homosexual lifestyle in public schools.” It called upon parents to keep their children home on Oct. 30.

According to the SPLC, as of last Friday, about 200 schools had cancelled their scheduled commemorations. “I was surprised that they completely lied about what Mix It Up Day is,” Maureen Costello, the Director of the Teaching Tolerance project of the SPLC, told The New York Times. “It was a cynical, fear-mongering tactic.”

The SPLC recently added the AFA to its list of active hate groups, which includes neo-Nazis, white and black separatists, and Holocaust deniers. The AFA, which is based in Tupelo, Miss., says its mission is to combat “increasing ungodliness” in America.