DEARBON (WWJ) - Officials at Dearborn Public Schools are investigating after a substitute teacher accidentally showed a pornographic video to a 7th grade U.S. History class.

Schools Communication Director Dave Mustonen said the teacher was trying to show students at O.L. Smith Middle School a Lewis and Clark video online, when the porn played instead.

Mustonen told WWJ's Sandra McNeill it's not clear why the school's filtering software allowed the explicit content to get through, and they're looking into it.

"I think our track record is outstanding. But, needless to say, one time is too many...especially at this age," he said.

"At the middle school age, students...you know, a lot of things are going on in their lives, and to see these kinds of images we understand can be very, very devastating, very upsetting."

Mustonen said an investigation completed by Dearborn police and the district into the March 13 incident concluded that the teacher meant no harm. No criminal charges were filed.

Regardless, Mustonen said the teacher will no longer be subbing in the Dearborn district.

"We have a very high standard for the people who work in our classrooms; and, just as a precautionary measure, we felt that it was best that this person not be in any of our schools," he said.

Officials said the kids were exposed to at least 30 seconds of pornography.

Mustonen did not release the teacher's name.