We know you can't be with your students constantly while they are online. However, if you take the time to instruct them before they're allowed to use the computer, you may keep them from being exposed to pornography, inappropriate adult-focused content, and even child predators who often lurk in chat rooms. Usage monitoring software is available commercially to help you with this task.
NASA will provide a wealth of resources that are safe, fun, and educational for your students. You can expect them to find reliable information on space-related topics, as well as games, Web quests, and even chats with NASA experts.
Please take time to review NASA's privacy and disclaimer statements.