A north-central Minnesota high school math teacher and adviser was charged Friday with having sex with one of his female students on at least three occasions, once at a Twin Cities hotel and two other times in his car.

Paul Joseph Johnson, 48, of Backus, Minn., was charged in Beltrami County District Court with third-degree criminal sexual conduct involving the 16-year-old girl from Bemidji, Minn.

Johnson was arrested Wednesday evening, appeared in court Friday and remains jailed.

A statement from Voyageurs Expeditionary School in Bemidji said Johnson “has been placed on unpaid administrative leave effective immediately” as the investigation continues.

Johnson’s bio posted on the charter school’s website said this is his fifth year at Voyageurs and added that he is married, and has three grown children and four grandchildren.

According to the criminal complaint, the girl told sheriff’s investigators that she had been “involved in a romantic sexual relationship [with Johnson] for quite some time” that included sexual intercourse.

One encounter occurred in October while Johnson was in a Twin Cities hotel while in the metro area for a teachers conference, she said.

The other two occurred in the back of his Toyota Prius in Beltrami County, she added.

The girl said that she and Johnson had many conversations in an online chat room and that their sexual relationship was among the topics.

Along with teaching math and being one of the school’s five advisers, Johnson also taught marketing, accounting, business ethics and speech classes, according to his school bio.

Voyageurs, with grades six through 12, focuses on public service and the environment.

Johnson graduated from St. Louis Park High School and Bemidji State University, the bio says.