Most new PCs these days are coming with Windows Vista on them. If you are a parent, especially if your children are younger, this can be quite a boon to you as there are many new security features in Vista that can be helpful to parents. Blake Handler has done a very nice job of setting out step by step instructions for parents. I highly recommend his post to you.
If you are responsible for monitoring school computers some of this will be very useful as well. You'll want to look more into the security and control that Windows Vista provides. These features will make life easier for a lot of school technology people.
There have been other articles on Windows Vista Parental Controls, but Blake's presentation is really the best. His guidelines are nicely laid out and easy to follow.
I also recommend the other Parental Guidelines Blake created. Links to those and more Parental Guides for Child Safety at http://securitygarden.blogspot.com/2007/05/parental-guides-for-child-safety.html