Router that can control when internet is on/off, based on time ranges?

I have suggested this to a couple parents before. Using a router like WRT54GL (linux variant) and installing something like dd-wrt firmware, or tomato firmware, you can control access at the router level, and EVEN add keyword filtering (blacklist words, sites, etc).

Great little routers, and if you want gigabit, just buy a gigabit switch, and plug it into your router as the last point out to your internet (unless your internet connecting is 100mbits+)

dd-wrt firmwares for Linksys routers have this option. I'm using it in my home network now.

I'm using a D-Link DIR-655 router, which includes an Access Control feature that will do what you want. Set up blocking based on schedules, ports, IP addresses and MAC addresses. It's an excellent router.

As far as I remember almost every Linksys router can manage time policies with its native firmware.