I'm a T.A. in a year 4 class, the teacher i work with gives me planning for a group of kids to work with each day. She differentiates for the class into 3 groups (higher, target and lower ability), we each teach the whole lesson to a group, one group works independently on a investigative task where the kids can support each other. The groups are rotated so that no group is left unsupported for more than a day-of course the children can ask for help, and we both pop over to the independent group to ensure they're on task. This seems to work well for us. We review progress at the end of the week and our conversations is used to inform planning etc.