By Suzanne Le Mignot

 (CBS) – A student was held down by fellow classmates and sexually assaulted by one of them.

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That’s the claim in a lawsuit filed by an angry Plano mother and her son. CBS 2’s Suzanne Le Mignot talks with the alleged victim’s mother.

“It’s been hard. It’s been hard,” says the woman.

She’s the mother of a Plano High School student. A recently filed lawsuit claims her son was held down by four other schoolmates, while a fifth student sexually assaulted him in the boy’s locker room.

She says the coach walked in and witnessed the attack.

“He walked in. He saw one person on top of my son, and my son had his pants down around his kneecaps, and the other kid was on top of him,” the mother says.

When she contacted the coach, “He told me that he was aware of this happening in other events, particularly during the football season,” she says.

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Scott Encher, the victim’s attorney, says the attack should never have happened.

“To me it’s unconscionable how something like this could happen and be allowed to happen,” he says.

The attorney for the school says there was immediate action.

The coach told a police liaison officer, the athletic director and principal.

The school attorney also says this appears to be the first incident of its kind. He plans to file a motion to dismiss the second amended complaint in this case, because he says, the school had no knowledge this was going on.

The victim’s mother says she in part is trying to prevent future abuse.

“This is sexual assault and I don’t want any other kid or any other family to have to go through what we’ve been through,” she says.

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A criminal case against the five students is pending.

Suzanne Le Mignot