At what point in education should rational thinking be taught?

I’ve come to the conclusion that rational thinking is as important as arithmetics for every day live, what I mean is, just as mathematics is vital for buying stuff at the grocery store, also knowing those fallacies used by marketing companies to make us buy stuff we won’t need, could help us to decide what to buy, or even for whom to vote for in the next neighbourhood association, or presidential election.

So, if rational thinking is so important, should it be taught together with other fundamental areas of educations? or at what point while we are acquiring formal education?