This works best with an older class of teens that have some knowledge of and respect for the environment. Or, better still, during an appropriately themed lesson on the environment.
It's fairly simple. If the class misbehave or get a question wrong, tap the "Cut" button and a tree will be cut down. If they behave well, or answer a question correctly, hit the "Plant" button and you can replant the tree! There are ten trees in total, so the class has ten chances to behave well or answer ten of your fiendishly difficult questions!