You can grow kamote or sweet potato tops in the kitchen. It also serves as a greenery of sort on the window sill.
Fill to three-fourth a convenient glass jar with tap water. Place a healthy tuber on the mouth of the jar. To keep it steady, stick three pieces of toothpick like a tripod. Add water daily as roots develop. Be sure to replace water weekly to prevent mosquitoes from breeding in the jar.
In a week's time or two you can start harvesting. At first allow the tops to extend. Just clip the leaves you need in your cooking. Rotate the position of the tuber towards the source of light, so that you will have more shoots, and greener and bigger leaves.
Now you have a dish garden for a whole month or longer. You can grow fresh onion leaves with this technique. Try it on garlic.
You see, this is simple hydroponics - soil-less gardening. It is introduction to the science of hydroponics and aeroponics. For school childre, why don't you try this as your project?
Read more about hydroponics and aeroponics. Happy gardening!