On Mix It Up at Lunch Day, schoolchildren around the country are encouraged to hang out with someone they normally might not speak to.

The program, started 11 years ago by the Southern Poverty Law Center and now in more than 2,500 schools, was intended as a way to break up cliques and prevent bullying.

But this year, the American Family Association, a conservative evangelical group, has called the project "a nationwide push to promote the homosexual lifestyle in public schools" and is urging parents to keep their children home from school Oct. 30, the day most of the schools plan to participate this year.

The charges, raised in an email to supporters this month, have caused a handful of schools to cancel this year’s event and has caught organizers off guard.

"I was surprised that they completely lied about what Mix It Up Day is," said Maureen Costello, the director of the center’s Teaching Tolerance project, which organizes the program. "It was a cynical, fear-mongering tactic."

The swirl around Mix It Up at Lunch Day reflects a deeper battle between the Southern Poverty Law Center, a civil-rights group founded 41 years ago in Montgomery, Ala., and the American Family Association, a Bible-based cultural watchdog organization in Tupelo, Miss. The association says its mission is to fight what it calls the "increasing ungodliness" in America.

The law center recently added the group to its national list of active hate groups, which also includes neo-Nazis, black separatists and Holocaust deniers.

Association leaders, in return, have gone on the offensive, calling the law center a hate group for oppressing Christian students and claiming its aim is to shut down groups that oppose homosexuality.

"The reality is we are not a hate group. We are a truth group," said Bryan Fischer, director of issue analysis for the association. "We tell the truth about homosexual behavior."

Although the suggested activities for Mix It Up at Lunch Day do not expressly address gay and lesbian students, the law center itself promotes equal treatment for gays and lesbians and that philosophy then informs the school program, he said.

"Anti-bullying legislation is exactly the same," Fischer said. "It’s just another thinly veiled attempt to promote the homosexual agenda. No one is in favor of anyone getting bullied for any reason, but these anti-bullying policies become a mechanism for punishing Christian students who believe that homosexual behavior is not something that should be normalized."

The program is not about sexual orientation but rather about breaking up social cliques, which are especially evident in a school cafeteria, Costello said.

In some schools, cliques are socio-economic. In others they are ethnic or religious or based on sexual orientation. By giving students a way to mix with other students, self-imposed social barriers can be broken down and bullying can be curbed, she said.

"Many of the targets of bullying are kids who are either gay or are perceived as gay," she said.

But the idea that the program is intended as homosexual indoctrination is simply wrong, she added.

"We’ve become used to the idea of lunatic fringe attacks," she said, "but this one was complete misrepresentation."

Parents who are on the American Family Association email list were encouraged to keep their children home on that day and to call school administrators to tell them why.

By Friday, about 200 schools had canceled, Costello said. But exactly why was unclear. Of 20 schools that had canceled and were contacted by The , only one chose to comment.

The Chattahoochee County Education Center in Cusseta, Ga., canceled because teachers were too busy trying to meet basic state teaching requirements, Principal Tabatha Walton said.

"The decision had nothing to do with taking a position on gay rights," she said. "We support diversity."

Although parents did complain to Kevin Brady, the head of the Avon Grove Charter School in rural Pennsylvania, the school is still planning to hold Mix it Up at Lunch Day for its 1,600 students.

Students will each be assigned a number and then paired up by school officials. The school has a large population of special-needs students who can feel isolated and thus benefit greatly from the program, Brady said.

The school started it a few years ago, inspired, in part, by the shootings at Columbine High School in Colorado and examples of bully-related violence that surfaced in schools around the country.

He said the email sent by the association described a program that had "absolutely no resemblance to what we do." Once parents understood how the program worked, they decided not keep their children home that day, he said.

"I think they feel they have been taken for a bit of a ride," he said.

© 2012 The New York Times Company