We used a similar system when my kids were early in their learning about money stage. 5 kids and banks all over the place.
The difference was that the tax fund actually was a choice of 2 pots. 1) Tax money that went for a rented movie or a pizza etc. and 2) the Disney fund. Sometimes the kids would put all of their taxes in 1 pot, sometimes they would split. It was an individual choice.
Also, charity was not an option. They had to put so much to others. We used a % type of breakdown. 12.5% for charity, 12.5% for taxes, 37.5% for shortterm (spend as you will, save for gifts etc.) and 37.5% for longterm (savings for college, or the Disney trip). My kids originally saved for 5 years, and then 4 years, and then 3 years, and . . . for the Disney trips.
A second thing (went into the Disney fund) that I did was buy bulk chips, popsicles, pop etc. The kids then bought off of
me instead of the local variety store. Also, any birthday/Christmas type gifts that I bought on sale went into
Mom's Store and the kids would buy (again) from me, rather than at the discount store.
As far as grades, we celebrate but don't reward high grades. We have a saying at our house. . .
The better you LEARN the more you EARN!