Well, I don't know about all of your crappy public schools, but mine produces more national merit scholars year in and year out than any other school in the state, public or private. Also, our average SAT and ACT scores are always near the top ten in the state. In fact, we have also been in the top ten nationally in average ITED scores in recent years.
Frankly said, in certain areas private schools may be a better plan, but in my district they're just a waste of money.