You're an awesome mom! I wasn't homeschooled, but at least we can do it for our kids.
So I have a few suggestions:
1. Hugelkultur bed- size it by how much your student can do. May be a lot of work.
2. Mini greenhouse - this can really increase food production on a small scale, and be made with recycled materials.
3. Mini rocket stove - Who doesn't like fire? My boys loved it when I made one of these with them out of a #10 can and spare tin cans.
BTW, indoor cooking is one the leading causes of respiratory (and other) problems in 3rd world countries. See
Ianto Evan's work.
4. Small swale system - again, size it to your student. FWIW, proof of concept can be better than perfection when teaching.
5. Seed starting - depending on your student, this could be simple or complex.