A South Carolina law banning sex education teachers from mentioning any relationships other than heterosexual ones — unless the talk involves sexually transmitted diseases — is fueling a climate of state-sanctioned discrimination, a federal lawsuit says.

The National Center for Lesbian Rights and Lambda Legal said the lawsuit filed Wednesday seeks to overturn the Comprehensive Health Education Act of 1988 as an unconstitutional violation of the equal protection clause of the U.S. Constitution.

The law, which mandates how sex education classes are taught, also subjects students to bullying and violence and stigmatizes a group that's already at a heightened risk of suicide, the lawsuit contends.

“By enshrining into state law that LGBTQ people may not be discussed on an equal basis as heterosexual people, the system of public education instructs all students that LGBTQ people are a dangerous, immoral class of people from whom other students must be shielded," according to the complaint filed in U.S. District Court.

“The negative impact is significant, communicating to teachers and students that there is something so shameful, immoral, or dangerous about “homosexual relationships” that they should not generally be discussed, the lawsuit states.

South Carolina's law also sends a message that students who are not heterosexual are specifically associated with sexually transmitted diseases, which fuels a hostile climate against them and puts them at risk of being bullied, the lawsuit states.

The lawsuit recounts the experience of one student from Greenville. He was in middle school when a classmate threw a Clorox wipe at him and “told him that he was diseased and that the stairway to hell was ‘rainbow-colored.'" The classmate then kicked him in the chest.

Harassment can have serious consequences. Nearly one-third of lesbian, gay and bisexual youth had attempted suicide at least once in the previous year, a survey from the Centers for Disease Control and Prevention found. That compares to 6% of heterosexual youth.

The law also says that any teacher who allows “a discussion of alternate sexual lifestyles” including “homosexual relationships except in the context of instruction concerning sexually transmitted diseases” can be fired.

State Superintendent of Education Molly Spearman, named as a defendant in the lawsuit, agrees that the law is on shaky ground.

She requested an opinion on its constitutionality from South Carolina Attorney General Alan Wilson. That opinion says “a court would likely conclude” that the law violates the equal protection clause requiring that people in similar circumstances be treated the same under the law.

“Whether we agree or not, the Constitution is the Constitution," Solicitor General Robert D. Cook wrote in the opinion.

“I agree with the arguments and evidence presented in the opinion,” Spearman said in a statement. “I also believe that parents should continue to have the final say in whether or not their child participates in health education curriculum.”

Parents can have their children opted out of the school sex education curriculum, said Ryan Brown, a spokesman for the state Department of Education.