My son started 7th grade at a 6th-12th school while he was still 11 (youngest 7th grader/only one with subject acceleration). He found the middle school environment, having eight different teachers for eight different classes liberating and enjoyable.
Bullying occurs, but does not seem to cut across grade levels. I think the school culture is such that peers would discourage picking on a younger grade student, as it isn�t considered sporting by the general population. School cultures vary greatly though.
