Oops. Forgot about that.
Well, if you're willing to include freely-available online resources that are nonetheless still firmly controlled by the copyright-holder, the SparkNotes people do have a page where you can read in HTML format the full information from some of their selected
SparkCharts, which are arranged into attractively bite-sized info-bits that the kids should have no trouble digesting.
And Fred van Lente and Ryan Dunleavy have full versions of selected stories from their
Action Philosophers and Comic Book comics, which they let you read free online or download as PDF in the hopes that you'll buy the entire collected editions (which certainly worked with me). They seem to be pretty enthusiastic about their stuff being used for educational purposes, and will probably be willing to let you pass the PDFs around if you just ask.
There's Pre-Socratic philosophers, John Stuart Mill, Rene Descartes, and Carl Jung. Informative and entertaining, and I think they'll appeal to younger readers.
Similarly, biologist Jay Hosler, who does science comics and has kids himself, has a couple of
1-page cartoons on his website which might be useful for illustrating concepts from course material. He's also got a
nifty blog where mentions he science stuff as it relates to comics (Skrull shapeshifters and biological mimics, etc.) and puts up extra illustrations, such as this
life-cycle of a liver fluke.
Hope this helps.