A former Maine kindergarten teacher who took pornographic photos of four of his students was sentenced to 16 years in prison on Tuesday.

Rob Mocarsky, 41, of Jackman, Maine, pleaded guilty in June to production of child pornography after officials discovered that, between 2007 and 2009, he had photographed four female students engaging in lascivious displays of their genitals, prosecutors said. The girls were five and six years old at the time.

The investigation began last December, when the mother of one of the five-year-old girls told the principal that Mocarsky had photographed her daughter in a miniskirt and halter top, The Bangor Daily News reported. The police searched Mocarsky's home and found an external hard drive containing photos of two girls in bikinis with the bottoms wedged in private areas, and another two girls in fairy costumes with no underwear.

Prosecutors said that all of the photos focused on the girls' genitals.

One mother testified that her daughter, now 8 years old, still refuses to sit for school portraits and won't let anyone she doesn't know photograph her.

U.S. District Judge John Woodcock told Mocarsky before his sentencing that he had dishonored the respected profession of teaching and countless teachers who work hard to transfer intergenerational knowledge to children. Your actions put their works under a cloud of suspicion. This is particularly true of a male teacher in the lower grades.

Woodcock then sentenced Mocarsky to one year more than the mandatory minimum of 15 years in prison, plus 10 years of supervised release. He could have sentenced him to as much as 30 years but said that even a 16-year sentence was extraordinarily punitive for a first-time offender, because the intent of the high minimum sentence is to punish people who produce child pornography that shows children having sex with adults.

This is the first time Mocarsky has been convicted of producing child pornography, but he was investigated for similar actions when he taught in New Hampshire in 1998. He allegedly took photos of students undressing, but he was not ultimately charged.

Mocarsky's lawyer, Robert Sandy Jr., said it was neither inappropriate nor out of the ordinary for elementary school teachers to use costumes in the classroom. But, while Mocarsky did frequently have his students play dress-up with princess and pirate costumes, that was not the subject of the investigation. The objectionable photos were those that were taken after school hours and focused on the girls' genitalia.

Mocarsky apologized for his actions shortly before Woodcock sentenced him.

I am truly sorry for what I thought and did, he said. I want to say I am sorry to each of the children and their families for the grief I have caused and to my colleagues and the community as a whole. I failed all of them and let them down.