Internet Timer Software

I'm looking for an app, freeware if there is one, that will disable a workstation's internet access during specific times without affecting other users. My daughter and her husband have several computers networked at home for their business, one of which is in their son's room. They want to be able to control his ability to access the web after, say, 9:00 pm until 8:00 am.

I've googled a bit, and there are some apps that seem to do this but also a lot of other things, and aren't free.

 

Honestly, the best way imo is via a router.

 

Thanks. I know nothing about routers but they do so I'll pass on the info.

 

On my routers at least i can specify the time allowed for a computer on the network to access the net.

I'm guessing most have this feature.