A teenager from Kentucky celebrated her 15th birthday last month by blowing out the candles on a rainbow cake while wearing a rainbow sweater. After her mother posted a photo from her birthday party on Facebook, the teen was expelled from her Christian high school.

Kayla Kenney was a freshman at Whitefield Academy, a private Christian school in Louisville, until she was expelled last week. Her mother said the school called her daughter's sweater and cake "lifestyle violations."

Kenney's mom, Kimberly Alford, told the Louisville Courier-Journal that she received an email from Whitefield Academy's head of school, Bruce Jacobson, expelling her daughter. He wrote that the picture she posted on Facebook "demonstrates a posture of morality and cultural acceptance contrary to that of Whitefield Academy's beliefs."

While the rainbow flag is a symbol of LGBTQ rights, Alford said when she ordered the cake, the design was described as having "assorted colors" and was not meant to have a deeper meaning.

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"Whitefield Academy's Biblical role is to work in conjunction with the home to mold students to be Christlike," the school says in its parent-student handbook. "On occasion, the atmosphere or conduct within a particular home may be counter or in opposition to the Biblical lifestyle the school teaches. This includes, but is not limited to, sexual immorality, homosexual orientation, or the inability to support Biblical standards of right and wrong."

In such cases, the school said, it reserves the right to refuse admission or "discontinue enrollment of a student."

Whitefield Academy told CBS News that the social media post about the birthday party was not the sole reason for Kenny's expulsion.

"She has unfortunately violated our student code of conduct numerous times over the past two years," the school said in a statement. "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."

The school said its teaching style is informed by "shared Christian values" and students are expected to "adhere to a lifestyle informed by our Christian beliefs." It did not elaborate on Kenney's past conduct violations.

The school also partially blamed Alford for her daughter's expulsion.

"It is unfortunate that one of the student's parents chose to post internal family matters on social media, and we hope our former student is not adversely affected by what her parents chose to make public about her situation," the school said.

Alford acknowledged that a school official found Juul pods in her daughter's backpack last October, which led to probation. But she said her daughter had been a model student since.

"Since October, there have been no disciplinary issues," Alford said. "There have been no academic issues. There has been nothing."

Alford said her attempt to appeal the school's decision was quickly denied. Her daughter was not allowed to finish the year, and is now attending a public school.

"She's adjusting really well, but she also seems stressed and overwhelmed at times," Alford told the Courier-Journal. "I felt like [Whitefield Academy] had a positive impact on her, but I just feel like those religious beliefs they are imposing now are very judgmental. That's not what I wanted for her."