http://www.bbc.co.uk/news/uk-england-32103991
The letter is here
http://www.audlem.org/newsroom/nantwich-education-partnership.html
Nantwich Education Partnership (who have sent the letter) are made up of both primary and secondary schools.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 letter is here
http://www.audlem.org/newsroom/nantwich-education-partnership.html
...Call of Duty, Grand Theft Auto, Dogs of War and other similar games, are all inappropriate for
children and they should not have access to them.
[...]
We need to inform you all of the actions we are advised to take and why:
-If your child is allowed to have inappropriate access to any game or associated product that is designated 18+ we will are [sic] advised to contact the Police and Children's Social Care as it is neglectful.