Dean Holmes, a student at York Catholic High School in York, Pennsylvania, put on a Black Lives Matter mask under his face shield at his July 28 graduation ceremony.

As students lined up before the ceremony started, the school's principal pulled him away in front of other students and told him to take off the mask, Holmes told CNN.

Holmes had previously been told by another school official to take the mask off, so he eventually relented for fear to not being able to walk across the stage, he said.

"I was so mad. I was shaking during the graduation, tapping my leg on edge...when it was over, I couldn't believe it," said Holmes.

York Catholic had opted to give every student a face shield instead of a mask for the ceremony.

Holmes's father, John, took to Facebook on Saturday saying that the school stifled his freedom of expression and jeopardized his health.

" ... the capricious action taken against my son demonstrates that York Catholic High School has miles to go before they can put the ugliness of unconscious bias and racism to sleep. As a parent I will not stand for my son being humiliated publicly, having his basic human dignity crushed on what should have been one of the happiest days of his young life," he wrote in the post.

Both he and his wife were also wearing Black Lives Matter masks during the ceremony, he told CNN.

No masks with messages for graduation, school said

In a statement August 2, Arthur Full, chairman of the York Catholic School Board, said it was standard "decorum" for students to not wear any messages and that any graduate would have been asked to remove it.

Two other students previously asked and were given permission to wear a solid color mask under the face shield, unlike Dean, Full explained.

"We wish to re-emphasize that York Catholic believes in the dignity of all human persons, and the equal treatment of all people. We encourage our students, faculty, and alumni to engage in personal conversation, continue to listen with open hearts, always strive for better understanding, and grow as a supportive community of love and respect," the statement continued.

Family says school didn't say no masks with messages

They were not told beforehand that masks with messages would be disallowed at the ceremony, the family said.

They also dispute several assertions in the school statement. According to the family, Dean had his mask on throughout the day and did not just put it on right before the ceremony, as the school said. Also, Dean was publicly told to take off the mask, not privately, as the school statement notes. The family also says Dean didn't have his temperature taken prior to the ceremony, despite the school saying he did.

The school declined to comment further beyond its original statement.

"The high school experience has been one thing after the other. He's had so many experiences that have really tried to belittle him and knock him down," said the father.

Going forward, Dean said