[GGardner]

You'd need about 0,00001ASA material for a 2 month exposure with a regular pinhole camera...

Are you sure that's right? I was hoping that reciprocity failure would (for once) be a big help in this kind of project.

I like all the ideas here. Cyanotypes might be fun, but require a real camera -- one nice thing about pinholes is that it's easy to give one to each kid, and have them run around outside trying to find the best place to put it. I also like the idea of sending home one image per student.

It's also too bad that the month long exposures are a problem, as I had hoped to tie in lessons about the seasons.

The good news: time to experiment!