Officials say 27-year-old Nicole Kurowski, a gym teacher at Tulpehocken High School outside Reading, surrendered Wednesday to face charges of institutional sexual assault. She was freed on bail.
Her lawyer didn't immediately return a phone call seeking comment Thursday.
State police allege that Kurowski had a sexual relationship with a male student both on and off school property during the last school year, and that some of the encounters took place during school hours.
Police said they recovered thousands of text messages, some sexually explicit, as well as photos, and they alleged that the two traded messages saying "I love you."
The district superintendent, Edward Albert, said he received a tip about Kurowski in early September and notified police and the Berks County district attorney's office.
"I think whenever you are in education, and you are trying to work with kids and you see something like this happen, it is disheartening," Albert told WFMZ-TV.
Kurowski has been suspended without pay pending the outcome of the case.