What it teaches
The parts of a plant and what each one is for. The job is the thing worth knowing: a child who knows the root drinks can work out why a plant in dry soil dies, and one who has only labelled a diagram cannot.
What to look for
This is the subject with the best homework attached to it. A bean in a jar of damp cotton wool shows the root and the shoot in about four days, and every question in this game becomes obvious afterwards.