Right idea in concept...but unfortunately, there are a great many kids who truly do give it all their effort in school, and still receive bad grades. It's not fair to leave kids like that out. Until schools begin giving grades for effort, this idea will never go anywhere.
I have three kids who know that the after school routine includes: homework, chores, 30 minutes playing outside, and THEN they can spend time on their PC's or playing video games. As a single parent, it's not really that hard to instill this routine in them. They know that bad grades = no games.