A Kentucky high school student's parents have filed a lawsuit against a Christian school whose administrators expelled the girl earlier this month after images appeared on social media showing her celebrating her 15th birthday while wearing a rainbow sweater and smiling next to a rainbow cake.

The suit, filed Thursday, contends that Louisville's Whitefield Academy expelled the teen, who is referred to as "K.K." in court documents, due to her perceived sexuality.

Kayla Kenney at her 15th birthday party. Kimberly Alford

“Essentially, the school expelled K.K. because they believed that K.K. was gay. As such, in Whitefield’s view, it would be difficult to “achieve the goal of [K.K.] becoming Christ-like," the suit states. "In so doing, Whitefield invaded K.K.’s privacy, defamed K.K., breached its contract with K.K.’s parents Kimberly Alford and Mike Kenney, and inflicted serious emotional distress on K.K. Certainly, in 2020 it is unbelievable that conversations like this one are still occurring — and that lawsuits like this one are still necessary."

While rainbows can have many meanings — in addition to being a meteorological phenomenon — they’ve served as a universal symbol of gay pride and acceptance since the late 1970s.

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Whitefield Academy declined to respond to requests for comment on the lawsuit. Earlier this month, however, the school told NBC News the rainbow-filled social media photo was just the last straw following two years of student code violations.

“Inaccurate media reports are circling stating that the student in question was expelled from our school solely for a social media post,” the school stated at the time. “In the fall, we met with the student to give her a final chance to begin to adhere to our code of conduct. Unfortunately, she did not live up to the agreement, and therefore, has been expelled.”

In an interview earlier this month, Kimberly Alford said her daughter had been on probation since October for “some behavioral issues,” including cutting class and being caught with an e-cigarette. But while she said school administrators claimed "in a roundabout way" that the probation wasn't about her daughter's sexuality, there were signs that administrators were singling the teen out for her "perceived sexuality."

Alford said after her daughter's probation, a school counselor had given the girl the book “Gay Girl, Good God,” whose author, Jackie Hill Perry, is a formerly identified lesbian who says God stopped her from being gay. Alford said her daughter and the counselor had been meeting weekly to go over the book before her expulsion.

A Jan. 6 letter to the teen's family signed by school head, Bruce Jacobson, said the rainbow-filled birthday photo "demonstrates a posture of morality and cultural acceptance contrary to that of Whitefield Academy’s beliefs.”

“We made it clear that any further promotion, celebration, or any other actions and attitudes that are counter to Whitefield’s philosophy would not be tolerated. As a result, we regret to inform you that Kayla is being dismissed from the school immediately.”

In Whitefield Academy’s student handbook, which can be found on its website, the school says a “homosexual orientation” household wouldn’t be considered “in harmony” with the school’s beliefs.

Alford said she wanted to share her daughter's story because she believes the teen was treated “unjustly” and she wants to prevent anyone else from being subjected to similar treatment.

“I just want to defend her in a graceful way. I want to stand up for my child,” she said. “Just treat people with kindness and love, and don’t be judgmental.”

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