The idea that the best way to help someone who is behind, is to put them with those farthest ahead, is completely insane. Yet that has been the policy behind affirmative action, behind integration-via-fiat, and behind eliminating tracking in grade school. It is not helpful to be in classes with people who are far ahead of you, as you won't get the practice on the basic, foundational topics that you need. You will be lost, and then fall even further behind. On the other hand, if you are grouped with people of your own ability, you have the opportunity to work hard, be among the best in the class, and feel much greater personal satisfaction. (See again how many nerds who despised gym class end up later liking casual ultimate frisbee games -- such games among people of similar ability level ends up being a lot more fun).