You can check with your ISP. I know Xfinity/Comcast now has the ability for parents to do just that. I think there would be separate logins for the kids so the adults are not restricted by the same controls.
Most routers have a management system where you can set the time of day a machine using it can have internet and the amount of time.
You can setup multiple conditions for set periods of time access the internet of each machine that connects to the router.
You can do this by logging into the router its self via its user name and password login.
Most routers support this feature. If you have one find the brand name and it`s model number and you should be able to find a manual for it in PDF format online telling you how to set things up.