A New Jersey Catholic school teacher repeatedly had sex with an underage student from her alma mater, prosecutors allege.

Roselle Catholic High School teacher Theresa Hrindo and the student — described as aged 16 or 17 — engaged in sexual acts on multiple occasions in Union County between December 2016 and February of this year, prosecutors say.

The Archdiocese of Newark, which has authority over Roselle Catholic, said Hrindo, 25, a part-time graphic design teacher at the school, was immediately suspended, CBS News reported.

The archdiocese reported the alleged indecent relationship to the prosecutor’s office, which launched a three-week probe, according to NJ.com.

“This is certainly something we’re very concerned about, and we don’t accept this kind of behavior or action,” said Jim Goodness, a spokesman for the archdiocese. “It’s very clearly against all school and diocesan policies, and plus, it’s against the law.”

Prosecutors did not indicate the student’s gender.

Hrindo, herself a 2010 Roselle Catholic graduate, has been charged with two counts of sexual assault, two counts of endangering the welfare of a child, and one count of hindering apprehension, according to NJ.com.

Hrindo, of Linden, was also charged with hindering for deleting incriminating photos and messages from the student’s phone, prosecutors said.

She was freed Friday after a night in custody, agreeing to have no contact with the student, and not to teach or supervise children. The most serious charge against her carries a term of up to 10 years in the slammer, prosecutors said.

“There’s a lot more here,” said Hrindo’s lawyer, Michael Brucki. the site reported. “I think things will come out.”