In school, your children are taught how to be safe online and visit age appropriate websites and games. If you allow your child to visit inappropriate games/sites you are breaking the law.
If you are worried about your child, remember you can always talk to your child's class teacher. The designated teacher in school to help with any online issues or questions you may have is Mrs Watson.
Below are a couple of documents you may find useful in ensuring your children are safe in the cyber world we live in.