What a good idea! I've never done that before, but I have read about the beans. Do you think sweet peas would work? Do you take the plants out and pot them up, once they've sprouted?

Sorry I'm not more help. This might be a good question for the vegetable forum, too.

I have not done it in a zip lock, but in a clear plastic cup. A wet paper towel was squished into the middle of the cup. I had a bean, corn and pea seed to compare the roots and cotyledons.
Another idea is to do sprouting seeds - alfalfa, sunflower, radish, cabbage, broccoli. Sometimes they are in health food stores and also seed companies like Johnnys and Pinetree sell them. The kids like to eat their own produce from the jar farms. Sprouts are ready to eat in less than a week.
This year the young 4-H gardeners made Grass Easter Baskets. Regular hard red winter wheat was sprinkled thickly on potting soil in a plastic lined basket. The grass is lookin' good in a week or less. The Easter baskets get a lot of attention.