The school district said Friday that it had suspended Ginnetti, who has been with the high school since 2007, with plans to fire her. She has been out of the school since last week, said Marc Neff, Ginnetti's lawyer.
Ginnetti surrendered Friday morning and was charged with institutional sexual assault, corruption of minors, and disseminating obscene materials to a minor, Montgomery County District Attorney Risa Vetri Ferman and Lower Moreland Township Police Chief Peter C. Hasson said in a statement.
According to an affidavit, police learned about the relationship from a phone call to ChildLine, a statewide hotline to report suspected child abuse.
The caller reported hearing a younger sibling, who had attended Lower Moreland, talking about inappropriate photos Ginnetti had sent the student.
Police later confronted the alleged victim and Ginnetti, and both acknowledged their relationship, the affidavit said.
In July, Ginnetti and the student met at a Starbucks store in Northeast Philadelphia, then went to an industrial park along the border of Philadelphia and Lower Moreland and had sex, police said.
Investigators also retrieved copies of the text messages, photos, and videos from the student's cellphone.
School district officials placed Ginnetti on administrative leave last week when they learned about the allegation, Superintendent Marykay Feeley said.
"We are now moving swiftly to terminate her employment and will take all steps necessary to ensure the teacher does not teach again," she said.
Ginnetti was arraigned Friday morning by District Judge Jay S. Friedenberg and freed on $50,000 unsecured bail.
Friedenberg ordered her to surrender her passport and barred her from contacting the alleged victim or having unsupervised contact with minors except her own children. Ginnetti also was to be placed on GPS monitoring.
A preliminary hearing is scheduled for next month.