And Direct Positive paper. More expensive than normal Ilford paper, but the contrast should be better, and you don't need to use a separate sheet for both the pinhole exposure and the print. However, it's fibre-based paper which is much more difficult to process - you need additional chemicals and very long washing times.
Oh yes that is a great idea for this project! Red safelight should be real easy to find. One sheet needed per student instead of two! Or you could let them try twice.