With his son onboard, dressed in his red cap and gown, WTMJ-TV reports the father landed an ultralight plane at Hamilton High School in Sussex on Saturday as a stunned crowd of hundreds watched.
Witness Alan Larson, who was there to watch his daughter graduate, says the plane circled, then landed on the front lawn near the parking lot as people streamed in.
The pilot told the station the Waukesha County Sheriff's Department issued him a citation. He did not want to elaborate further.
The ultralight remained on the front lawn as the commencement ceremony took place. Father and son left the school the same way they arrived.