The program isn't using the game to teach music, it's just meant to engage student in the arts, to get them interested in music. Which, I think, is a fantastic idea. Sure, Guitar Hero and Rock Band would do the same thing, but including instruments they are both more expensive.
The program is, in part, a reaction to the D.C. School Chancellor's new policy to make sure every school has a music teacher on staff. The Wii music program will eventually be in 50 cities throughout the country.
Maybe Harmonix or Activision will take a page from Nintendo and test out a program that would introduce younger children to music through their games. I know that's why Tristan is studying classical guitar now.
Nintendo Wii Debuts in D.C. School [Fox DC]