Group Policies using Win2000 server

Hi, i work for a school district and we are trying to implement group policies for the users especially for the students since teachers they don’t want for students to change screensavers, install programs, use the win media player.. change desktop background. those are some examples what are they want me to do. I’m new at group policies i try to setup a policy on the server but when i login at the workstation the policy doesn’t apply so i don’t know what i’m doing wrong. Can any one help me find information or provide me with some examples of setting group policies at the server please.

Thanks in advance..