(CNN) Staff at a Chicago elementary school made a boy leave the building on a cold March day, coatless and in short sleeves, then lied about what happened, according to a lawsuit that alleges a pattern of abuse and harassment by the staff and the boy's classmates.

The fourth-grader had been bullied from the time he enrolled at Fiske Elementary School at the start of the school year, his mother, Yvonne Pinkston, told journalists Tuesday. But the school staff "failed to take any action" to protect the boy and "even became abusive towards him," according to the complaint filed in US district court in Illinois on Monday.

The lawsuit against the City of Chicago, its Board of Education, the school's principal, a counselor and a security guard alleges a hostile educational environment, saying the school lacked proper policies and training for discipline and didn't investigate allegations of misconduct. It also alleges battery, excessive force and intentional infliction of emotional distress. The plaintiffs are asking for a jury trial.

In surveillance video from the school, shown by the family's attorney at a news conference Tuesday, a man identified by the family as the school security guard yanks the boy into an office. A few minutes later, a different camera shows the man ushering the child toward an exterior door.

The principal, the counselor and the guard "created a barrier" to keep the boy from staying in the building, the lawsuit alleges. The surveillance video shows two adults following the boy to the door as he exits, and other adults watching it happen.

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