Former Wings School pupil Harvey Benson alleged that during physical restraints some staff could be “forceful and violent”.
During one, he said a staff member kneed him in the ribs and barricaded him in a classroom.
Mr Benson said he made three reports to police in 2019, two reports to his social worker in 2019 and one report to Ofsted in 2022, detailing concerns for other pupils.
In his first report to police, he said the officer responded: “Well that’s how I treat my kids if they were misbehaving.”
Mr Benson, who is campaigning for CCTV in care home communal areas and bodycams for staff, said: “The police and the authorities dismissed every single one of us for years as troublemakers… that we were making up these allegations to cause trouble.
“It’s a catastrophic failure.”