tracking

It's occurred to me that when you play sports, you like to play with people who are more or less at the same skill level as you are. If you're playing with people who are better than you, they'll resent the mediocrity of your play, the errors you make, and that you might even lose a game for them. (For an individual sport like tennis, it gets boring being easily defeated time after time.) If you're playing with people who aren't as good as you, the opposite is true, and you're going to resent their incompetence. If you're playing with people at about the same skill level, it's more fun, and the outcome will always be in doubt.

If that's true for physical endeavors, it's also true for intellectual endeavors. Students should be in classes with people of about the same ability level in the different subjects. Otherwise, they'll resent having to waste time trying to get the 'slow' students to 'get it.' On the other hand, if you're in a class with people who are better than you, you'll feel swamped and inferior. This is no good for anybody. If you're in classes with people at about your ability level, students will feel comfortable, and the learning will proceed apace.