i gotta say, first off, congrats man! this is impressive that you tried it, good to see that somebody who can actually enforce this, is enforcing it!
however, i'm quite pleased that it managed to work. i have 3 main criticisms however
1) i would guess that the age is a big factor. as kids as younger, this system would probably work even better. but i think as the children get older (particularly with college education) this may be less effective.
2) this system worked on the principles of bribery. the children were getting a reward for doing what they were meant to do in the first place. if you a permanent teacher for the class, all day achievements/all week achievements would be a much cheaper way of doing this.
3) my biggest concern is that these kids may have been interested because it was something new. the novelty of the idea may wear off eventually.
i would be interested in seeing what further work is done on this, possibly addressing these issues.
once more, nicely done!