I disagree.
The uniform for the graduation ceremony was cap and gown. If he wanted to wear his uniform, he could have done so under the cap and gown.
From the article: "It now appears the school made a mistake, and Liberty Union High School District Superintendent Eric Volta acknowledged it, saying a review of state law showed Fletcher was within his rights.
“It has become clear that Harland Fletcher may have the right to wear his U.S. Army Dress Uniform at his graduation, and on behalf of the Liberty Union High School District, I publicly apologize to him and his family for the incident,” Volta said in a statement released late Saturday and posted on the school’s website."