BURLINGTON, Vt. (AP) — A former math and science teacher at the Vermont Academy is going to prison for 30 years after pleading guilty to a variety of federal child pornography charges.

Brant Nelson, 49, of Saxtons River, was sentenced Monday in U.S. District Court in Burlington.

Nelson was fired from his job at Vermont Academy around the time of his January 2012 arrest, the U.S. attorney’s office said Wednesday.

Prosecutors said Nelson possessed child pornography and took young girls to New York to participate in sex acts with him and another adult.

The investigation started in 2012 after police say they received a report that Nelson possibly had images of child pornography on his computer and had an interest in very young girls.

He admitted having child pornography on his computer, engaging in sexual contact with a young girl, taking pornographic pictures of his child victims and posting them to the Internet and sharing with other pedophiles the child pornography he made, according to court records.

Nelson was convicted of six counts of production of child pornography, one count of possession of child pornography, and one count of interstate travel to engage in sexual act with a minor, and one count of interstate transportation of a minor for sexual activity.

At sentencing, Judge Christina Reiss said Nelson’s criminal conduct was the worst she’d seen in her years as a state and federal judge.

“Nelson’s conduct was horrific and among the worst ever prosecuted by this Office,” said U.S. Attorney Tristram Coffin.

Nelson’s attorney declined comment.