Auto shutdown and restart (XP)

I have a network of about 50 computers in a school. To conserve energy I'd like to shut down the PCs overnight, during weekends and holidays. On a school weekday they'll also need to be turned on, at say 6:00AM.

Is there a simple, in-built way to issue a single command from the server to do this? Is there a script available? Is there a utility out there?

I know in Control Panels there is something called scheduled tasks, is this of any use?

There is various 3rd party software that does it
or
http://www.online-tech-tips.com/computer-tips/remote-shutdown-command/

You can shutdown in various ways but starting it up will require 3rd party software.

Ask the caretaker to turn them on when he opens the school up in the morning.

There is a device in Netto, to shutdown items via remote control...Why would computers in schools be left on all night? Surely telling the pupils, turn off your computer, would be enough?

Can you use the 'Wake on LAN' in the BIOS and send a wake-up signal?

shutting down is easy: either a policy from the servers (say within group policy if you have a domian), or simply a scheduled task using Windows' built in shutdown executable. At a command line type "shutdown /?" and this will list the various parameters you can use with it. Make a batch file with the command and then set it in scheduled tasks to run at whatever time you want.

Waking up, now this is the hard part. As previously mentioned, wake-on-lan is the normal method, but this often requires a fair bit of knowledge about it and networking depending on your setup, or a lot of money to install a complete solution.

I'd have a rummage in the BIOS on some of the machines: Quite often you can set a time for the pc to start it self up in the mornings, and depending on the model can set it to only do this on specified days (my work pc turns itself on at 8:30 every weekday).