You are providing the equipment. It is between you and your teacher. But since it is a simple recommendation and could mold the tank and also teach so many students about the biology of whatever you decide to keep or whatever plants you decide to keep...I don't see how this is a loss since it is in your teacher's classroom. He might be actually able to teach the students biology, I.E pearling of plants, mating of shrimp, mating of fish, keeping of high light/low light plants in a contained experiment. Seriously the possibilities are endless and explainable to the board of education.