Affirming Vitaliy's suggestions I'll say something beyond his
comprehensive answer and to a certain extent more specific. A
great mathematician S.Banach used to say (maybe as a joke) that
children shouldn't be taught mathematics early because that
would be a too sharp tool for them. There is an obvious analogy
and this is why children shoudn't be taught Mathematica too
early. I'm affraid the events such as C.Wolfram's talk at the
TED conference make some kind of delusion and I feel similarly
when reading (pointed out by J.M.) an interesting discussion
Will it rot my students' brains if they use Mathematica? Though
in general I agree with the statements therein and find
Mathematica a great computer system, however one should
carefully consider WRI employees' arguments concerning such a
delicate issue as teaching. To point out helpful resources if
one's aim is to be capable doing more than just press the
button, it is a good way to read a clear and concise compendium
by Richard J. Gaylord: Mathematica Programmi