I think there is. Have you checked all the brain training items. Try big brain academy and crosswords
Is There A Game On Nintendo Ds For Learning English?
I think there is a game coming out on February 2009 about learning how to speak and read English for the DS
Have a look on amazon, they sell a number of learning games for the DS including Mind your language and Learn English. If you have access to the internet there are a range of game based learning resources available. You might want to look at BBC Bitesize