A former West Philadelphia middle-school teacher was sentenced to 15 years in federal prison Monday for persuading one of his 12-year-old students to send him sexually explicit photos.

Christopher D. O’Sullivan, 32, taught at Belmont Charter Middle School on the 4000 block of Brown Street until his crime was discovered by the child’s parents in 2019. He pleaded guilty to charges of enticing a minor and production of child pornography last year.

FBI agents found sexually charged images of the child and at least 100 other young boys on his phone and laptop when they searched his Kingsessing apartment, prosecutors said.

“The defendant’s crimes … are abhorrent, outrageous, and disturbing,” Assistant U.S. Attorney Michelle Morgan wrote in court filings preceding Monday’s hearing. O’Sullivan “was in a position of trust, and took advantage of a child’s vulnerability in order to exploit him in a most egregious manner for his own sexual gratification.”

Text-message exchanges between O’Sullivan and the 12-year-old paint the former teacher as a cautious manipulator, constantly coaxing the student into more and more extreme behavior — at times offering him gift cards in exchange.

He held himself out as a mentor equally comfortable talking about video games and camping in conversation with the boy — even as he harangued him for illicit photos, in-person sexual encounters, and details about his experiences with masturbation.

“I just wanna make sure it’s something you actually WANT to do,” he told the boy in one July 2019 exchange, in which O’Sullivan sought a “sexy video.”

Whenever the boy pushed back, the text messages show, the teacher laid on the pressure.

“I wanna see if you’re all talk or actually a man of your word this time,” he told the child in a later text conversation.

Prosecutors have also alleged they found several explicit photos of naked infants and teenage boys that appear to have been taken when O’Sullivan traveled to South Africa in 2013.

After the boy’s parents found a photo of their child’s genitalia, which he had sent to O’Sullivan on their son’s phone, they alerted the school and O’Sullivan was arrested shortly after.

He has remained in the Federal Detention Center in Center City ever since, his attorney Michael Harris Fienman said Monday, “concentrating on his rehabilitation.”

The 15-year sentence U.S. District Judge Nitza I. Quiñones-Alejandro imposed Monday was the mandatory minimum she could have given O’Sullivan as a result of his conviction on the child-pornography charge.

In addition to the prison term, Quiñones-Alejandro ordered O’Sullivan to complete 10 years’ probation and pay $5,200 in restitution to his victim after his release.