A Christian high school student in Kentucky was expelled after school administrators saw a photograph from her 15th birthday party in which she was wearing a rainbow sweater and smiling next to a rainbow birthday cake, NBC News reports.

“She was happy. She looked beautiful,” the teen’s mom, Kimberly Alford, told NBC affiliate WAVE of Louisville. “Of course, as a mom, I took her picture blowing out her candles, and I posted that on my Facebook page.”

Alford said that shortly after she posted the photo, she received a letter from the head of Whitefield Academy, where her daughter, Kayla, was a freshman.

“The WA Administration has been made aware of a recent picture, posted on social media, which demonstrates a posture of morality and cultural acceptance contrary to that of Whitefield Academy’s beliefs,” the letter, signed Jan. 6 by the head of the school, Bruce Jacobson, said. “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.”

Read the full story on NBCNews.com.