The more the better
I believe the problems relating to large classes and mixed ability groups belong in the same category where ELT discourse is concerned. In the early days of the communicative approach, these were presented as major teaching challenges. This, in my view, is because these problems have been dealt with from a teacher-centred classroom approach, where the teacher has a hard time dealing with too many kids, or those who are very different.
I very strongly believe that every class of more than one student is mixed ability and large. It’s not the number or the difference between children that determines the challenge, but what the teacher wants to achieve. If you just deliver (favourite word: impart) material, it does not really matter if you do it for 5 people or 500. If, on the other hand, you aim at giving every single student in your class at least one meaningful moment they take away with them, even two students per class might be a tall order.
I believe that the “problem” with mixed ability and large classes ceases to exist the minute you stop looking for what you can teach to every single student, and instead start looking at ways of turning your classroom into a workshop where every student of any ability has a role.
I know this sounds far too simple and unrealistic to many teachers struggling day-to-day with thirty, forty or more students, but I strongly believe that the minute we relinquish our determination to teach our students and decide to create an environment where students learn from processes taking place in the classroom, acquire the skills of integrating into a group and defining and representing their niche (what they’ve got to offer to that particular group), the size of the class becomes an advantage.
This also allows teachers to become part of the learning process — which in turn makes their work much more fun and meaningful as well.
If the material is not a grammar structure but instead is a challenge, a project, or a task students have to complete by negotiation, discussion, and collaboration, then even super large classes can become learning communities.
If the teacher does not deliver material but coordinates and facilitates the work done in and by groups, learning won’t depend on how many of the students the teacher can reach the ears of.
If technology is used appropriately to complete tasks, information will not exclusively derive from the teacher, and students learn independence and self-reliance.
If different forms of classroom arrangement and working solutions are applied, students will learn the immensely important skills of self-representation, negotiation and being part of a team.
All of these are essential skills to be successful not only in learning a foreign language but also in integrating into the world of work.