The cost of many, if not most kids in public schools is highly subsidized by people who may never have had children. The last time I checked, a few years back, tuition at the closest private school to me (A Lutheran school) was $6500 per year, per student.
If you have 2 kids, your cost would have been $13,000 per year. Unless your property taxes exceed that amount, your cost would have gone up to school those two kids, at least in my example of the Lutheran school.
Of course a less expensive option would be to home school, if you can afford to have one spouse not work outside the home.
I know I'm going to get some flak for that last sentence, it's inevitable.
You can also send them to private school up until high school. They would have a solid foundation by then and can resist the moronic teachers.
You also have to stay on top of what they are learning in school. I think most parents assume their kids are learning the right things in school.