(AP) – A former Joplin middle school science teacher will spend 28 years in federal prison for sexually assaulting a girl over nine years and recording some of the assaults.

Forty-year-old Charles Dominic Gastel of Carterville also will spend the rest of his life under supervised release when he leaves prison.

As part of a plea agreement reached Friday, Gastel admitted that he sexually assaulted the victim for about nine years and videotaped some of the assaults. The victim, who is now 19, said the sexual acts began when she was 10.

The Joplin Globe reports an affidavit says Gastel’s son saw a video on his father’s laptop computer that depicted a sexual assault.

Gastel, who taught at South Middle School, has been in federal custody since his arrest in July.