A substitute teacher at a Dearborn middle school reportedly played a pornographic video for 30 seconds in a class of seventh-grade history students who were expecting to see something on Lewis and Clark.

WJBK-TV FOX 2 reports the incident happened on March 13, and that the school district is blaming a “glitch” in technology.

David Mustonen, communications director at Dearborn Public Schools, told the TV outlet that the substitute teacher was “unaware this video was there.”

“In this particular instance, it appears there was some sort of loophole -- one time too many -- but very isolated,” he told FOX 2. "Are we looking into this particular instance? Are we making sure this doesn’t happen again? Yes, absolutely.

“Do we need to scrap everything and start over? No, nowhere near that.”

A letter that went home with the 29 students in the class at the time of the incident called the ordeal an “unfortunate and rare occurrence.” While police have closed the case and are not pursuing further action, the outlet reports the substitute from the incident will not be asked back to the district.