Shutting off Internet Access after 10PM

Question

My teen-age sons are at the age where they want the independence of making their own choices, and resent my telling them what to do and when to do things. I am trying to encourage them to plan their play time and work time so that they get their work done before it gets too late and "have to" stay up late to finish (because they spent their time doing non-school stuff on the Internet).
The message that the Internet will be disconnected at 10PM has been heard load and clear now that dad pulls the cable out of the DSL interface, stuffs the cable in his pocket and goes to bed. They are getting much better at front-loading Homework and leaving discretionary web surfing etc. until later. After 10PM (with the Internet disconnected, but the Server still running) they can still access their user accounts, type their papers, and print. But the Internet is not available, and game time and chat time is over.
I am fishing for a more automatic way to "turn off the Internet at 10PM", so that I don't have to stay up until exactly that time and physically pull the cable and carry it away.
I am running Server 10.3 at the moment, but have Server 10.4 DVD and am planning to install it sometime soon. Workstations are running 10.4, and are in a largely public area (not buried in out-of-the-way places with no potential for oversight).
I welcome all suggestions, including those not involving computers at all!

Answer 1

All this cabling and re-cabling caused me to re-configure my Routers and Switches, which threw my Internet connection offline. In attempting to get it working again, I went back to the actiontek Router that Verizon FIOS provided originally. The actiontek's power supply had failed, and I had dropped back to a previous Router. Verizon later sent a replacement Power Supply, even though the unit was out of warranty.
When I went to configure the actiontek Router, I noticed that there were a lot of options to restrict access for just certain users, and to restrict actions based on time. There were options for both content-filtering (which I am not currently using) and Firewall-based restrictions, many of which could be based on time-of-day and day-of-week.
Once I set the Router's date and time, and allowed it to be updated from a network time server on the Internet, I was able to set up a set of FireWall restrictions for every day of the week. At 10 PM, it disallows traffic through the Firewall, and keeps it off until noon the next day. Now everyone in the house knows the Internet shuts off at 10 PM, and no manual Intervention is required. If you have not completed your homework by then, your Internet time is over regardless.
Verizon FIOS customers and actiontek Router users reading this should check for these features in your Router -- you may already have the solution in hand.