Police in Chestnutt Hill Township, Pa., charged Lawrence Liero, 18, with disorderly conduct and open lewdness, a third-degree misdemeanor, after he exposed his rear to two girls visiting Pleasant Valley High School, WBRE-TV, Wilkes-Barre, Pa., reported Thursday.
The Pleasant Valley School District suspended Lawrence and banned him form participating in his graduation ceremony.
Chad Liero, Lawrence's father, said school officials went too far.
"I definitely think they went way overboard by what was done," he said.
"Now it's starting to get pretty scary," he added, in reference to the criminal charges.
Lawrence could face up to one year in prison for open lewdness charge, WBRE reported.
Superintendent Doug Arnold said the district left it up to police whether to investigate or press charges.
"It's a violation of law not to keep your clothes on. It's unacceptable in school," he said. "I don't know that anybody would condone mooning someone."