William Carruba, 19, a Granite City High School senior, was initially denied permission to wear the kilt to his prom by school officials and the Granite City School Board sided with the officials Tuesday, the St. Louis Post-Dispatch reported Wednesday.
The school board ruled the kilt was a "non-traditional" garment and unfit for the prom.
"We must adhere to our [dress] policy," Superintendent Harry Briggs said. "To do otherwise would be reckless on our part."
Carruba said he will abide by the decision.
"I understand full-heartedly," he said after the meeting. "I'll just ... wear pants."