I've worked for SCIENCE, a multi-disciplinary weekly journal, for over 15 years. Probably a bit too technical for school aged younguns but if you can find the WEB site for Bill Nye the Science Guy you may be able to find all kinds of sources that will help you. He's entertaining and educational too. 'Ask Jeeves' is a good search engine for specifics. If you need more than you can find let me know & I'll see what I can do.
Laurie