Teach your children well

Long break since last post, but since I am on vacation for the next few days I thought I would hammer this one out since its been rattling around in my head for the last few days.
I may be (really) late to the party, but I am starting to fully understand the duty all parents have to teach their children how to think.  This is a bit different than educating and certainly is not teaching them what to think.  Both our kids are deep into various parts of American history and its somewhat scary to me what they are being taught and what’s being omitted.  For example, evidently Christopher Columbus was a pretty bad man.  Never mind that he discovered America (or at least re-discovered it) and mapped the waterways of the Atlantic and Pacific.  He later became a governor of an island and was too mean: he actually punished people that stole things (by cutting of their hands…and sometimes their heads).
I am not trying to make a case for Mr. Columbus’ sainthood.  However, I am starting to see that history can often be used to support modern agendas, even in the very conservative Catholic school system that my kids go to.  So, what is a parent to do?  Of course I could try to tell a more balanced story about the good things that Columbus did.  The problem with that is that only fixes the immediate problem.  And it ignores tha hardest part of being a parent: you aren’t always going to be there.  This argument is normally applied to helping your kids say no to things that will obviously hurt them (drugs, sex, etc).  It’s harder to teach them to think critically and challenge their teachers.
The best I have been able to do is tell them that there are two sides (at least) to every story and that they should always try to understand as much as possible if they are trying to make a call about serious things like who’s right and who’s wrong.  I figure that approach has a double bonus: it will keep them from jumping to conclusions / believing everything they hear in school AND it will give them more motivation to dig into the things that really interest them, hopefully giving them a lifelong love of learning.