I would understand "ability grouping" as a self contained group with more organizational and curricular separation, and "cluster grouping" as putting several similar kids together in one heterogeneous classroom with lots of other kids, with curricular differentiation happening as much or as little as it happens for everyone.
You may want to google Susan Wjnebrenner to find out about he research on making cluster grouping successful.

Last edited by Tigerle; 06/14/17 01:56 PM.