The 36-year-old, named as Sabrina Z. by the newspaper La Stampa, appeared in court on Monday, charged with coercion.
The incident dates back to June 2010, when the teacher, who worked at a technical college in Ivrea, a town in Piedmont, took the girls to a swingers' club in Turin, where they were reportedly subjected to “bodies entwined on the sofa”.
The teacher was charged with coercion after allegedly threatening one of the girls if she told anyone about their night out.
An accomplice, Michele, 46, who drove the girls to the club, also appeared in court.
He told the judge he didn’t know that one of them was underage. The other girl was 19 at the time.
“I never ask a woman’s age,” he reportedly said, while winking at the judge.
Rumours of the night out soon started circulating within the school, prompting the principal to report the teacher to the police and then later fire her.
Claudio D'Alessandro, the lawyer representing the older girl, said the case was not about the night spent at the club, but what happened afterwards between the teacher and the girl.
“It was the coercion that triggered the case,” he was quoted by La Stampa as saying.
The charge is punishable by up to five years in prison.