BOSTON — A federal appeals court yesterday upheld the dismissal of a lawsuit filed by Lexington parents who objected to same-sex families being discussed in their children's elementary school classrooms.

Tonia and David Parker of Lexington sued school officials in April 2006 after their son brought home a book from kindergarten that depicted a gay family. Joseph and Robin Wirthlin joined the suit after a second-grade teacher read the class a story about two princes falling in love.

In yesterday’s decision, the 1st U.S. Circuit Court of Appeals agreed with a judge who ruled in February 2007 that parents' rights to exercise their religious beliefs are not violated when their children are exposed to contrary ideas in school.

"Public schools are not obliged to shield individual students from ideas which potentially are religiously offensive, particularly when the school imposes no requirement that the student agree with or affirm those ideas, or even participate in discussions about them," the unanimous three-judge panel said in Parker v. Hurley.

Jeffrey Denner, an attorney for the parents, said they were disappointed with the ruling and were considering appealing to the U.S. Supreme Court.

"Normally, when kids are taught certain things, they believe it to come from on high," Denner said. "I think this influences the way they think in very, very direct ways and becomes functionally indoctrinating to them."