To answer the question back up the page a ways, most kids don't get to garden at school because up North you have that nasty cold weather called "Winter". The kids are out of school for summer, which is most of the growing season for most of the country, and Canada. There's not enough time in fall, and maybe 2 months in spring when you could grow anything, right?
Down here in the South we can start a garden in September and harvest in 3 months, time to make Stone Soup and clear out the beds for the holidays. But we have to pick early, short maturity tomatoes and such to make sure we actually have stuff to pick in time for the soup. Then the new semester starts in January, perfect timing to plant cool-season stuff like lettuce, carrots and broccoli. We have to wait until late Feb. (or this year, mid-March! ) to put in beans, tomatoes, peppers and the like.
Still here we are at the end of March and we only have 9 weeks before school is over. We'll be able to harvest potatoes, beans, carrots, peppers, onions and maybe tomatoes (if it will just warm up!) and our cool season salad stuff is nearly over already. The lettuce is getting bitter and starting to bolt. Still, it's all a learning experience, and the kids just LOVE it. We talk about everything from Photosynthesis and chlorophyll to plant life cycles with the big kids to 'what does a leaf do' with kindergartners. Bugs, water, sun, composting, interplanting, worms, what things are good for the garden (good bugs, bees, butterflies, snakes EWWWW) and bad for the garden (chemicals, cold weather, rabbits, chewing caterpillars). Every weed is an opportunity to ask "why do we have to pull out weeds?" or "what IS a weed?", every bug and worm sparks a question. So much fun!
As far as getting hands dirty, I agree, it's wonderful to dig in with your bare hands. But it's a problem for school kids when they are only in the garden for 1/2 an hour, then they have to go back to class. Also a bit of a safety concern, thus the gloves go on whenever the kids come to the garden, and it really helps them to feel free to plant, thin out seedlings, touch bugs and plants and look for worms.
Fun fact, did you know most Florida kids don't know how to put on gloves? Warm weather is such a problem . . .
