I think you should not sink to his level.
You are the boss now so it is your responsibility to act like a competent, capable, intelligent boss. That means NOT being vindictive.
Your incompetence as boss by doing what you suggest would reflect badly on you and would not go unnoticed by the rest of the workforce. As a competent, trained manager, you are are aware of the negative impact that could have on productivity, right?
If you want to prove this ex-teacher right, just be the sort of @rse-hole you suggest in your question.
If you want to prove him wrong, you only have to show that you have risen above all that stuff when you were a kid and that you are a mature, successful person - exactly what he thought you would never be.
The guy is already squirming so he is paying for his past. You do not make yourself look any better by rubbing his nose in it,