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DUNCANVILLE (CBSDFW.COM) – A former Duncanville teacher began a ten year prison sentence Friday, convicted of having an affair with a student.

It’s an unusually long sentence for the crime, but one Sandy Washington believes her son’s teacher deserves. “I almost had a stroke. Or a heart attack. I don’t know,” she recalls.

Her son was 17 when she says he first told her about the two year old affair with his algebra teacher, Elizabeth Ramsey.

“She was actually writing letters saying he was in tutoring,” said Washington. “They were having sex at school. They were having sex at her house.”

Washington remembers she was initially ecstatic when her son, who has Asperger’s, began to make friends his sophomore year at Duncanville High. She says she later learned Ramsey had taught him to buy marijuana, make brownies and give them away.

“He finally had friends and they weren’t true friends. That hurt,’ said Washington.

She says the affair only ended after Ramsey’s husband came home and nearly caught the two. Washington says her son had a psychological breakdown.

“She discarded him like a piece of trash,” she says.

Ramsey pleaded guilty to having an improper relationship with a student in order for a charge of sexual assault to be dropped. She received a ten year sentence, longer than most teachers convicted of the same crime.

“They usually end up in probation, but when there are extenuating circumstances like in this particular case, 10 years makes sense,” says attorney Pete Schulte, who reviewed the case for CBS11.

Washington now warns parents not to make the same mistakes she did – trusting too much, questioning too little.

“Be nosy, be consistent, be overbearing. These are your children.” she advises.

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