If at all possible, HOMESCHOOL. If the circumstances don't permit that, then try AFTERSCHOOLING. It would involve giving the kids a few minutes each day of what is missing in schools; civics, real history, non-PC science, etc. It could be in the form of videos, historical fiction, etc. You could also try memorization drills for math, etc. Tie it to some sort of reward system!
What is amazing is how little time it takes for your kids to learn at home what they are missing in school. Every 30 minutes of home learning time equals over an hour's worth of school work!
Our daughter's public grade school has been excellent on American history and civics (and even more so after 9/11/01.) I wouldn't assume that every public school is falling down in this regard.
One of the biggest problems is the so-called "education reform" bill recently passed by the US House & Senate. So much emphasis is given to standardized testing that even excellent history programs in "at risk" schools are being swept aside in favor of test preparation.