Tammie, this site has been very useful to me for our PTO newsletters go to school.discovery.com/clipart/index.html
You will find many school related clipart that I think you will enjoy.
I don't know about SCHOOL specifically, but I always go to the MicroSoft Clip Art Gallery Live. They have tens of thousands of graphics available. The download is designed to work with Microsoft Office products. The URL keeps changing, so I usually just go to the home page (www.microsoft.com
) and type "Clipart" in the search window.