At school this year my class planted dun pea and buckwheat sprouts. Quick-growing (plants in 5 days), the kids could observe roots and shoots growing on a daily basis.

Even after sharing seeds with the other classrooms, there were plenty leftover, courtesy of our neighbor Joanne. The rest got moved to the boat along with a little bit of potting soil. I now plant them once a week and soon enough we have micro-greens for salads, sandwiches, etc.