Schools in many areas are very busy teaching classes about how to put a condom on a banana, how to make change and balance a checkbook, how to appreciate diversity, third world culture, etc. ad nauseum, EVERYTHING BUT AMERICAN HISTORY.
Speaking as a recent high school graduate, I've never been taught how to put a condom on a banana, or how to appreciate diversity or the most foreign, bizarre cultures. I WAS taught to write a check--in 6th grade. Never ran into that afterwards.
Meanwhile, I was required to take four English classes, three mathematics classes, a government class, an American history class, two foreign language classes, and a few other such academic requirements that I've already forgotten due to lack of interest.
The problem with the public school system isn't a PC curriculum, it's a lack of interest on the part of the students. The Constitutional Convention is boring, and besides, half the students are text messaging the other half.
Take away the students' justification for thinking "I don't need to know that! When will I ever use that information?" and you'll see public education improve.