Restrict IE 5.5 Website Access

Managing workgroup environment for student computers in a training lab environment. Would like to restrict access to based on Instructor’s specific website(s)needs. Is there any way to restrict access to specific web sites using IE 5.5, group policies, or 3rd party software? Would like to implement from each workstation. Intent is to restrict Internet roaming and prevent downloads or viruses while students are in the labs.