Johnson, 51, has been placed on unpaid leave by the Union Grove High School Board.

The investigation began in Racine County after the sheriff's office received a letter concerning rumors that Johnson had sent inappropriate text messages to students.

Investigators did not find those messages, but according to court records, they described Johnson's two phones as "suspiciously clean."

A subsequent search of one of Johnson's phones allegedly uncovered images of young girls that investigators determined were sexually explicit.

Johnson has been charged with two counts of possession of child pornography.

A preliminary hearing is scheduled for next week.