We do some kind of seeds/planting every year either at the start of Spring or for Earth Day. I have had mixed luck with different flowers and vegetables. The most success we have had is with beans that we start off by germinating in a plastic bag taped to my window. The kids love this as they can clearly see the bean start to sprout. Once they are growing nicely we transplant to small pots and I send them home shortly after. The last time we did this my own children actually did get beans to eat.
Here is a link:
http://www.saps.org.uk/primary/teach...-a-plastic-bag