The tapes were found in three duffel bags hidden above the ceiling tiles in the classroom. There was no indication that any students had seen the tapes, which were discovered by maintenance workers on Tuesday.
Class had let out for the year last Friday.
The unnamed teacher has not been named, but taught at American Fork Junior High School.
The matter was referred to police, but Lt. Darren Falslev said there was nothing illegal about the 30 videos. Falslev did say he thought it was inappropriate to store the tapes at a school. No charges are expected to be brought against the teacher.
Falslev said the teacher cooperated with the investigation and apparently just didn't want to keep the tapes at home.