I need a program that will allow me to track my teens online activity

I recently adopted a teenager, who has been involved in inappropriate and dangerous behavior on the internet. I need a way to review what websites have been visited and to review chats and emails. Restricting computer usage has not worked as there are computers at school. I just want to protect my child from predators. Even though my child is a teen, developmentally and socially is more like a young child (8 or 10).
Please help.