A former teacher at Providence Day School will spend more than 13 years in prison after he pleaded guilty to sexually assaulting a boy he had been baby-sitting, according to Mecklenburg prosecutors.

Tristan Russell, 29, had been a teacher at Providence Day's afterschool and summer programs for two years, school officials said.

He was arrested last August in connection with the assaults on the boy, who is younger than 13. Prosecutors say the assaults did not happen at the southeast Charlotte school.

Russell pleaded guilty on Monday to three counts of statutory sex offense, said prosecutor Leslie Cooley.

Superior Judge Bill Constangy sentenced Russell to between 13 and 16 years in prison. After he's released, he must register as a sex offender and submit to electronic monitoring for the rest of his life.

Russell's attorney, Anthony Monaghan, could not be reached Monday.

Russell met the victim and his parents when he worked at Trinity Episcopal School, Cooley said. Later, after Russell started working at Providence Day, he baby-sat the boy to make extra money.

"The victim had disclosed to a friend that he had been sexually assaulted by the defendant," Cooley said. "The defendant was interviewed and confessed to multiple sexual assaults on the victim over a period of several years."

The assaults happened from 2008 to 2010.

After Russell's arrest, officials at Providence Day and Trinity Episcopal notified parents, but no other victims have come forward.

Jennifer Howe, a spokeswoman for Providence Day School, said officials there sent "an email to our parents when we found out all the facts." She said no Providence Day School students were involved in the incident.

"In a situation like this we also have a duty to make sure that there aren't any other victims out there," Cooley said. "The schools looked into it - both schools and CMPD - and as of right now, no one else has come forward."