A comment made to me about this which has frosted my husband to no end it that the bighter ones become an incentive to the underachievers, they can help them. My husband's attitude to that is "Fine, where's her paycheck if she is expected to teach the others"
I don't know the context of the comment so I may be off base right here, but tje brighter ones can become an incentive in my own class. BUT the way I use it menas being an INSPIRATION, not as a tutor. Last year I had a girl who went up 3 grade levels in one month in reading. You can bet I made a big deal out of it. Pretty soon a bunch of other students wanted to be just like her. They went home and made sure they read each night and soon started to improve rapidly. Not many got up where the girl was, but many made very good individual progress (2nd grade or above--I teach first grade). Only one person didn't get a second grade level, but she was very close and had made amazing progress too. I love having above-average reading students. It sure doesn't hurt.