A Mora High School teacher used his school-issued iPad to take more than 100 sexually oriented photos of female students — apparently without them knowing — and he also carried on a monthslong intense flirtation with a 16-year-old student, according to charges.

Benjamin C. Rossow, 38, of Mora, was charged in Kanabec County District Court on July 27 with 17 felony counts of interference with the privacy of a minor. Rossow was jailed and then released on bail. The school board accepted his resignation Monday.

Messages were left with Rossow's attorney Wednesday seeking a response to the charges. Rossow was jailed last week and has since posted bail. A woman who answered a phone call to Rossow on Wednesday declined to comment. Rossow's wife, Sara, works at the high school as a social worker.

According to the criminal complaint:

A 16-year-old girl's mother told the Sheriff's Office in May that she suspected her daughter was in an "inappropriate relationship" with Rossow. The girl told her mother that she and the teacher had been sending messages to each other outside of school hours.

The girl told a deputy that she and Rossow, her debate class teacher in the previous semester, were texting 20 to 30 times a day for several hours every afternoon and evening. Sometimes they'd be in touch until 2 a.m. She said that she and Rossow had conversations about cuddling and slow dancing together. One time, he brought up kissing her.

She said she also met the teacher at an abandoned home, but "nothing inappropriate" happened, the girl said.

At school, she continued, they would have lunch together in his room and she visited him during study hall and at other times.

Authorities searched Rossow's classroom computer, school-issued iPad and his cellphone. They found thousands of texts and e-mails between the girl and Rossow from last September to mid-May. They included the teacher complimenting her appearance and a request that she send him a photo of her in her prom dress.

The search of the iPad revealed 114 photos taken in class of girls, some of them in low-cut shirts, bending over and others taken of girls' buttocks while wearing tightfitting clothing. The photos are dated as early as November 2013, and continued for months.