"...All grades would be averaged and everyone would receive the same grade..." That's the communist manifesto not socialism. The experiment is flawed. Should rerun it with min 50% guaranteed and compare with previous results. Although even this has issues as the result ignores important extraneous influences.
Think overall there would be a significant reduction in the overall average as those just looking to get through maximised their personal economic benefit by investing their time in other fields. ...But... There would still be a significant % who will be looking at their overall results and still put in.