David Andrew Borghesani, 29, of Northampton, Pa., is charged with unlawful contact with a minor and corruption of minors.
According to the Lehigh County District Attorney's Office, Borghesani sent sexually explicit photos of himself to three students.
Prosecutors say he also sent a sexually explicit video of himself to one of the girls and asked her for sex.
Borghensani no longer teaches at the school. He resigned in February.
He was arraigned Tuesday.