If you feel the need for blocking software, there are several differnet programs available to choose from. SurfWatch, Cybersitter, and Cyber Patrol are all commercially available programs for restricting access to certain materials. But parents or teachers have to be involved in setting them up and making sure they are used.
Personally, I think it's a lot more effective to just talk to the kids, make them aware of the risks and enforce your values through observing what kids are doing while they are on the computer. If they are offended or come across offensive materials, they should let you know so you can inform the postmaster of the offending site (use the e-mail address of the offender but substitute "postmaster" in the address for the name of the sender) or the webmaster of the offensive site for World Wide Web pages.
