A former teacher at a northwest Indiana high school has been charged with persuading several underage girls to send their naked photos to him by cellphone. Jon Erik Lilly of Cedar Lake was arrested Wednesday on federal charges of possessing visual depictions of a minor engaging in sexually explicit conduct. He couldn't be reached for comment because his phone number was unlisted. Lilly allegedly talked four girls into sexting with him when he taught at Morton High School in Hammond. Court records unsealed Wednesday say a school official caught him sitting with a female student between his leg in November.