How does one control PCs and monitor what is on them?

My Dad owns a school with about 20 computers and VERY unreliable administrative staff. They are lazy, use the computers to do jobs for outside people, and would take any opportunity to slack off. He needs to control each computer so that they do not mess about with the work computers. These computers do not have internet, they are just on a LAN.

Is there a way of doing this in a way that cannot be disabled by the users? A tool like VNC is easily disabled. Also, he needs to be able to browse the files as well as see the desktop and a log of past activity on the desktop.

None of this process is to be hidden, it’s to be generally known that the school computers are public to all staff and whatever you do on them is clearly visible. Like I said, there is no internet, so nobody is supposed to be doing private stuff here that would be a cause for concern.

I was thinking in terms of some type of VMWare or something like that.

Also, one other problem is that my dad is not very computer literate and he does not have a sysadmin that he can trust. So the system, once setup, has to run on its own and not need much admin help. Also, this is windows XP and not Linux.