I think your essay is good and I wish you a lot of luck. I wish I had your libertarian spirit when I was in public school.
Did the “government is an externality and should abdicate” argument actually sit well with your teacher?
You might not have enough time in your presentation, but it may be helpful to give a short refutation of “public goods” theory which is always used to justify the glaring inefficiency of public schooling. In fact, one might venture to call their defense of it a little too… predictable. [:O][6]