Not sure how good an idea badges like that are in general though. Although, yes, they probably do act as an encouragement for many children to do the activities associated with them, they do seem to promote their use as a social scale (i.e. more badges is better).
Then there's the question of when do you award a particular badge. If you decide you need a achieving a certain performance in that particular area for that badge then surely you risk disaffecting the lower achievers. If you decide on a more varying scale depending on personal ability then you risk making the badges look meaningless.
At least with the scouts there is enough variety that you can cater to an individual's strengths. However, I'm still not convinced by them.