Authorities say the elementary school teacher told the children that it was a game. Once inside his third-grade classroom, they say, he blindfolded them, gagged them and set cockroaches crawling on their faces.
And then, Mark Berndt photographed them, creating hundreds of images that would eventually lead to his arrest, police say.
On Tuesday, Berndt, 61, was sitting in jail on charges that he committed lewd acts on 23 boys and girls, ages 6 to 10, between 2008 and 2010. None of them complained about Berndt's behavior, authorities said.
Police and school officials only learned of it when a film processor found Berndt's photos more than a year ago. Since the discovery, the school district fired Berndt and police put him under surveillance.
"If it wasn't for the film processor, this could still be continuing today," said Lt. Carlos Marquez of the Los Angeles County sheriff's department.
Berndt was arrested Monday at his home in Torrance and was being held on $2.3 million bail.
Some parents picking up their prekindergarteners at the school on Tuesday complained that officials at Miramonte Elementary School in South Los Angeles should have notified them when the photos were found.
"My concern is why, if the principal knew this in advance, why didn't he inform us?" said Gloria Polanco, the mother of a second- and a third-grader. "How long has he been doing this?"
The probe began after the film processor, who is required by state law to report suspicions of child abuse and molestation, turned over some 40 photographs to authorities.
Searches of Berndt's classroom and home turned up about 400 photographs depicting children, though the number of pictures may not be the same as the number of kids. At least 10 youngsters in the photos have not yet been identified.
Some photos showed Berndt with his arm around children or his hand over their mouths. Some photos showed children with live bugs the size of hissing cockroaches on their mouths or faces.
Kids reported being fed something distasteful. A blue plastic spoon and container found in the trash in his classroom tested positive for Berndt's semen, authorities said.
Police recommended the children in the photos be tested for sexually transmitted diseases.
Authorities could have arrested Berndt on misdemeanor charges when the investigation began but chose to build a stronger felony case, Marquez said. He could get a life sentence if he is convicted.
Berndt, who has no previous arrest record, was placed under surveillance and is not believed to have had contact with children during the investigation. The childless bachelor lives a few blocks from two parks and an elementary school.
The incidents occurred during school hours but not all the children were his students, Marquez said.
"The reason some of the kids are not his students, per se, is that during the lunch breaks or recess, he'd go out to the playground and entice them back to the classroom," Marquez said.
Los Angeles Unified School District Superintendent John Deasy said he was notified of the investigation last January and removed Berndt from the classroom the same day. The school board then fired him, he said.