Here is my take on this. It's not the best decision by the school board but it's not a big deal either. Lets face it the kids who "learn" this are going to form their own opinions regardless of the teaching anyway. We don't teach racism in schools yet we still have racists. The kids probably won't even remember it 5 minutes after they've supposedly 'learned' it. And even if they do remember it i highly, highly doubt they will use it as a basis to believe it. Their belief in the law as un-American will come from their peer group and families. Not the school. So please lets not make this more than what it is.
A minor misjudgment with no lasting effects outside of making the person enforcing it feel good about themselves.