30-year-old Benjamin Emmott pleaded guilty to 13 counts of privacy violation.
He was charged with secretly shooting videos up women's skirts.
Penobscot County Superior Court Justice Ann Murray rejected a plea agreement, which would have sent Emmott to jail for six months.
After hearing from some of the victims, Murray decided on the nine-month jail sentence, loss of Emmott's teaching certificate, and 10 years on the sex offender registry.
"There were many more victims, some of which we weren't able to identify," said Asst. Penobscot County District Attorney Marianne Lynch. "Some of which, we talk about a statute of limitations, so after a certain period of time we're not able to bring those. And again this was the one thumb drive we found."
Emmott's admitted activities were discovered after someone found a computer thumb drive in a car previously owned by Emmott.
Some of the women whose privacy was violated were co-workers, while others were random women he recorded in local department and convenience stores.
In court, Emmott apologized to the victims and his family.
Some of the images dated back to 2008, while some of the victims appeared as young as 14.