Read other letters about this article
qu1j0t3: Mathematica is a disaster for anyone but the most gifted high schoolers. I don't even recommend it for non-technical majors in college. It is syntactically very picky, yet has very soft variable typing. It is also essentally a compartmentalized and extensible language, which is great for a very technical person building their own tools, but is terrible for dynamic groups (e.g. in classrooms) experimenting and wanting to share code.
Wolfram has tried to get into the K-12 market. Several teachers I know (calculus, diff eq) have played with MM and concluded that it's basically good for demos during lecture but not for the students. There are many excellent packages for K-12 math and programming, some of which have been mentioned here.