I think the Laffer curve(particularly how it varies in width depending on whether it is a corporates, sales, or income tax), the various types of taxes, the basics of supply and demand, gold standard/bimetallism, unemployment, and inflation would be enough.
I think basic concepts are more important at the grade school level because they incorporate a lot of ideas that are used in day to day life (and often used incorrectly)
1.Diminishing returns
2.Distinction between long term and short term
3.Marginal vs aggregate thinking and the related concept of equilibrium or the equimarginal principle
4.Scarcity and trade-offs.
5.Facts vs opinions (positive vs normative)
6.The concept of 'there is no such thing as a free lunch' or more broadly and more importantly (but more difficultly) the concept of second order, third order (and so on) effects.
7.Related to second order...effects, the concept of network externalities and the related idea of compliments and substitutes, and the further related idea of how ideas, concepts, products... build off of previous ideas, concepts, products...
So, for instance, one interesting discussion utilizing these things would be did the 'Laffer Curve' actually introduce anything new to economics given that the idea that taxation levels could be made so high that they discourage economic effort was already known (President Kennedy commented on this years before the Laffer Curve came along) and given that Laffer himself never placed any numbers in his curve?
Of course, if the Laffer Curve should be taught, students should also be reminded that there is also a point to the left of the maximum where total revenues to the government go down when taxes are lowered, a point that all of today's promoters of supply side economics seem to have forgotten.
