This site is geared toward middle schoolers and has a lot of health information. They can find out more about nutrition by going to the Body tab and clicking on the "More on Body" link at the bottom of the page. This takes them to a site that has information about proper nutrition and what they can do to be healthier. This is a good site to use for researching nutrtional requirements.
This site is from PBS kids has students using a virtual kitchen to solve a puzzle and do experiments. It also has experiments the kids can do in their own kitchens and post the results