Container gardening allows you to grow plants in difficult situations, using different gardening types, many of them very suitable to schools. The blog Container Gardening is completely dedicated to making your growing experience a successful one.
One of the ideas that they explore in great detail is how to grow a vegetable garden in plastic bottles. They have some clever ideas and good advice. There are exhaustive details about containers, soil, drainage, seeds, etc.
This might make a good school project that could then be taken home.