I would agree, tomatoes are a great plant for teaching how to take cuttings. Also mint or succulents. They’re all super easy to propagate.
I guess corn would be good to teach about genetics and basic plant breeding if you use coloured corn, as you could show how each kernel was individually fertilised and is genetically different to its cob mates. Violas or pansies could work too, as they’re supposed to be very promiscuous 😉.
Trying a three sisters planting could teach how plants can be grown together to help each other out.
Beans are fun. They can be used to teach the sprouting on wet paper towels method, about natural fertilisation methods as they fix nitrogen in the soil, and how much variety there is that just can’t get unless you grow them yourself 😊 They only sell the green French beans in my local supermarkets, but I can grow purple, yellow or speckled.
Pretty much any edible plant can teach how much better home grown stuff tastes.