An ex-Florida teacher who secretly recorded female students changing clothes in the classroom will spend more than a decade behind bars.

According to the Tampa Bay Times, Mark William Ackett received a 15-year-prison sentence Monday after pleading guilty to 324 counts of video voyeurism. Each of those counts represent the 125 victims, most of whom were filmed while they undressed in his fashion design classroom.

“There’s so much suffering in this case by so many different people due to the actions of the defendant,” Judge Laura Ward said during the sentencing hearing. “There’s very little I can say today to make any of that better.”

Ackett was first arrested several years ago, after a 17-year-old student who was changing in his classroom noticed a box on a shelf that had a light shining through it. The girl reportedly looked inside the container and found a cell phone that seemed to be recording. Upon further inspection of the room, the girl discovered a second hidden phone and immediately reported them to the principal, who then alerted police. 

Authorities say the 52-year-old man, who has worked as an educator for about 30 years, had collected and edited hundreds of nude and partially nude photos and video of the victims, including Eva Applebee, a teacher who had worked with Ackett for 12 years at Bloomingdale High School.

“What Mark did was not an isolated lapse of judgement but calculated and deliberate criminal acts,” Applebee said in court. “Mark groomed and chose his victims – gaining their trust and then taking advantage of them.”

A parent and five students also testified in court, describing the anxiety and anguish they’ve experienced since Ackett’s crimes were revealed. One victim, whose name was not announced in court, described herself as a standout on the school’s track team, when Ackett was serving as coach. She told the judge she completely quit the sport in wake of Ackett’s arrest. Another victim claimed she had stopped going to church, as she had started attending Bible studies at Ackett’s home when she was only 12.

Ackett’s legal team argued he had suffered from voyeuristic disorder that stemmed from childhood trauma. The 52-year-old reportedly wept in court, expressing regret over his actions. 

“I wish I could go back and change what I did, or do something to make amends but I know that I cannot,” Ackett said, as reported by ABC News. “I feel especially ashamed of what I did because you treated me with such care. Some of you confided in me your fears and problems, and many of you consider my classroom a safe place to escape the problems that you face. I will never forgive myself for turning something that should have been a fond memory for you into something that you would rather forget.”