A third grader with ADHD and PTSD suffered pain and trauma, lawsuit alleges, highlighting problem of hundreds of young children being placed in restraint

“You can do what we have asked you to do, or you can suffer the consequences.”

The threat is issued by a police officer in Covington, Kentucky, who is caught on video as he grapples with an individual he is attempting to restrain. The officer, carrying what appears to be a holstered gun around his waist, tells the person as he holds him: “You don’t get to swing at me like that … Now sit down in the chair like I’ve asked you to.”

The individual in question is an eight-year-old boy, weighing 52lb and standing 3½ft tall, who suffers from ADHD and post-traumatic stress disorder. When the police officer stands back, it becomes clear in the video that the boy has been handcuffed above the elbow – his wrists are so tiny that the police officer has placed the boy’s arms behind his back and locked the handcuffs around his biceps.

“My arm! Oh God. Ow, that hurts,” the boy can be heard, crying out in pain. He was kept in handcuffs for about 15 minutes, school records suggest.

The shackling of the elementary school pupil, as well as a nine-year-old girl in the same school district, is the subject of a federal lawsuit issued on Monday by the American Civil Liberties Union and the Children’s Law Center. It accuses the Kenton County sheriff’s department and the police officer in question, deputy Kevin Sumner, of violating both federal and state laws that prohibit the restraint of elementary and disabled pupils in all but the most extreme situations.

The lawsuit says that the handcuffing of the boy, named only as SR, caused him “pain, fear, and emotional trauma”, as well as exacerbating his disabilities. “Plaintiff SR experienced physical pain and significant emotional distress during the handcuffing,” the legal action states.

In a second incident, the lawsuit also describes the handcuffing of a girl aged nine by the same deputy sheriff who has duties that span several public elementary schools in Covington. The lawsuit alleges that the girl, identified as LG, was handcuffed by Sumner on two occasions around her biceps as punishment for behavior related to her special needs.

The forced restraint of very young children is a recurring problem in public schools across the country where increasingly police officers, known as “school resource officers” but employed directly by the local sheriff’s department, are used to discipline unruly pupils. A report from the US Government Accountability Office catalogued hundreds of incidents between 1990 and 2009 of school kids – most of whom had disabilities – who had been forcefully restrained.

The report identified 20 cases that ended in death.

In the wake of the GAO report, the Kentucky board of education introduced new rules that restricted use of handcuffs only to those situations where a “student’s behavior poses an imminent danger of physical harm to self or others”.

A spokesman for the Kenton County sheriffs department told the Guardian that they had not yet seen the ACLU lawsuit and could not make any statement.

The distressing video capturing the handcuffing of SR was filmed by a staff member of the school who has not been identified. The incident occurred on 13 November 2014 after SR experienced difficulties in the classroom related to his diagnoses for ADHD and PTSD.

He was taken to the vice-principal’s office and after the boy tried to get away from the office the police officer was called. During the 15 minutes in which he was kept handcuffed, Sumner is heard saying: “It’s your decision to behave this way. If you want the handcuffs off, you’re going to have to behave and ask me nicely.”

In a statement, SR’s mother said: “It is heartbreaking to watch my little boy suffer because of this experience. School should be a safe place for children. It should be a place they look forward to going to. Instead, this has turned into a continuing nightmare for my son.”