Well, first of all cooking doesn't need to have a heat source. There is so much you can do with raw food (salads etc) and this often makes things simpler.
But, if you are going o be regularly cooking in your classroom you will pretty soon want to have a heat source of some kind.
When I first started cooking in my classroom I made use of the schools Baby Belling hotplates. It is a simple way to start, but there are quite a few disadvantages.
* They take a while to heat up and controlling the heat can be really difficult.
* They take an age to cool down afterwards and I consider this a real hazard as even though the plates don't look hot they could cause a severe burn.
* By the time they are put on a table the hot plates are at a completely wrong height for the child to safely cook with.
* Cables trailing over the floor cause a real trip hazard.
Then, after volunteering with Square Food Foundation, I was introduced to cooking with a simple butane gas cooking stove and it was a revelation.
* They heat up quickly, but also cool down quickly as well.
* They are easily controllable.
* There are no cables to trip over.
* They are incredibly light ( I can easily carry 6 in out of a school on my own - something that can't be said of a Baby Belling).
* They are cheap (about £10), and pretty reliable considering the price.
I have been using the Camping Gaz version of this stove for over a year now and they have been equipment I can rely on. I always carry spare gas canisters with me and I have found that if you buy the canisters in bulk they can be bought for £1 each.