My teenage son was staying up super late on his laptop doing teenage internet things (porn & gaming I assume) and f***ing up in school, so we put parental controls on the router so that the internet would be turned off from 11 pm to 7 am.
This of course impacted my wife and I, because we lost internet access during those hours too. Grumble grumble damn kids, etc.
Anyway, he was way more tech-savvy than we were, so he was able to bypass the parental controls, and stay on-line as late as he wanted. So the end result of the parental controls was that the parents didn't have internet, but the teenager did.