A Schools and teachers often group children by ability to give specific support or to extend learning, or, in many cases, simply to coach for key stage tests. There isn't space here to discuss all the issues, but this shouldn't be the case all the time.
Working in mixed ability groups, for example, for speaking and listening activities, drama, working at the computer, discussing texts in group reading or collaborative writing, offers excellent opportunities for children of all abilities to work together. And, for example, if children can't read texts independently, they can be given access in other ways prior to a discussion.
During research projects and development work at the Centre for Literacy in Primary Education, we've found that taking part in reading and writing activities with more experienced peers benefits less experienced or reluctant readers and writers. The effect on their self-esteem, motivation and skills shouldn't be underestimated. The key is to create activities which are open-ended and creative enough for all children to benefit.