Issues with classroom differentiation

In my top year 10 class, although basically ability streamed (with a few exceptions in the class for social reasons), I have thirty students. Behaviourally there are few problems but as the year has progressed I have 8-10 3AB MAS/MAT bound, 3-4 3AB MAT, 8 2CD bound and 10 2A bound.

This means that as the course continues, student goals are different for each block of students. For some it is so important that they master content now (such as 3D trig and bearings) to leave time for new content introduced in 3AB MAS and 3AB MAT. For those entering 2CD next year, they have a few bites at the cherry, the content is seen for the first time this year, consolidated next year and mastered in the following year. For the 2A crew they do not ever have to master some of the content, but by spending extra time on the basic concepts of more difficult areas of mathematics (especially algebra), they have a higher chance for success as they need to learn very little new content over the next two years.

With such broad groupings though, students are feeling frustrated that they cannot reach the 3A MAS bound students and some have asked to be moved to lower classes (better to be a big frog in a little pond, than a little frog in a big pond). Yet I have resisted this as there are transition issues this late in the year moving students between classes and no guarantees of success in lower ability classes. I have tried to redirect them to before and after class tutoring sessions.

I just thank my lucky stars that we streamed at the start of the year (thanks to one of my colleagues pushing for it). If there were 1B students in the class as well as behavioural issues the class would have had no 3A students at all.