Funny story about limiting access online.
My first wife and I divorced when our kids were entering their teenage years. To say my kids are bright would be an understatement. Anyway, my ex realized the kids needed a computer for school. So she bought an HP desktop model with a printer. She spent the entire evening setting up all the parental blocks and passwords. Plenty of frustration involved (she called me 3 or 4 times for help) and she was worn out by the time it was done. But she felt good about having the computer and having set up all the protections and limitations to keep the 11, 12, & 13 year old safe. She goes to bed.
Next morning she gets up and finds Post-It notes all around the screen listing all the passwords for every block and every access point. The boys spent a couple of hours hacking the entire system. According to them, they didn't go anywhere bad. They just wanted to see where all that stuff was stored.