Mixed ability is usually considered to be a problem. But is it? Could there be some advantages to having students of different levels and abilities in the same class?
I think we have to try to find the bestof each situation.
It's true that we can have some difficulties on teaching with a mixed ability, but there are advantages,too:
You can identify the best students and ask them for help; we coul mix the students, to learn from each other.
In my opinion, all the students are good at a topic: listening, grammar, reading... maybe, the best choice would be create different team works depending on the activity