My son's second grade class has "cluster grouping" for math. Before they accelerated him to fifth grade math a few weeks ago, this was his experience: two math periods in the day. The morning math period, everyone received the lesson of the day (I actually sent in fourth grade work for him to do during this time). The afternoon math period, the cluster group sat at computers and did math games. So not a punishment for the cluster kids. But the rest of the class is not happy that they have to drudge on with their work while the cluster group plays games on computers. The cluster group actually receives no specific instruction. They are just electronically babysat.