Head teachers in Cheshire have warned parents they will report them to the authorities if they allow their children to play computer games rated for over-18s.
The letter was sent by the Nantwich Education Partnership group to parents from 16 schools in the county.
The heads claim games such as Grand Theft Auto and Call of Duty contain unsuitable levels of violence.
They warn parents they could be reported for neglect in some cases.
The heads state that playing such games or accessing certain social media sites can increase early sexualised behaviour in youngsters and leave them vulnerable to grooming for sexual exploitation.
Mary Hennessy Jones, the head who drafted the letter, said: "We are trying to help parents to keep their children as safe as possible in this digital era.
"It is so easy for children to end up in the wrong place and parents find it helpful to have some very clear guidelines."
Prime Minister David Cameron announced this month that adults in positions of responsibility could face prison sentences of up to five years if they failed to report allegations of the neglect or abuse of children.