The investigation began when a film processor gave authorities some 40 photographs depicting blindfolded children in a classroom with their mouths taped shut.
A sheriff's department statement said Mark Berndt, 61, was arrested Monday at his Torrance home and remained jailed Tuesday on $2.3 million bail.
The district attorney's office said Berndt has been charged with committing lewd acts with 23 boys and girls ages 7 to 10 between 2008 and 2010.
Berndt worked for more than 30 years at Miramonte Elementary School in an unincorporated area of south Los Angeles before being fired.
Some of the photos showed Berndt with his arm around the children or with his hand over their mouths.
Other pictures depicted girls with what appears to be a spoon up to their mouths as if they were going to ingest a clear-white liquid. A blue plastic spoon and container found in trash in Berndt's classroom tested positive for semen, the statement said.
Some of the children's mouths and faces had large, live Madagascar-type cockroaches on them, according to the statement.
"It makes you sick to your stomach," Los Angeles Unified School District Superintendent John Deasy told KTTV Fox 11 News, which first reported the arrest.
The teacher was immediately removed when police informed the district and was fired, Deasy said.
No student ever came forward to report the abuse, he said.
More than 80 current and former students and school employees were interviewed for the investigation.
The sheriff's department said a search warrant served on Berndt's home led to the discovery of more than 100 similar photographs depicting children.
A DVD depicting adult sexual bondage activity "which mirrored the bondage-type photos of the children" was also found during the search, the department said, noting that the adults in that video were not identified and those images are not a crime.
The department said about 10 children seen in photos have not been identified.