Hear hear.
Perhaps many to do not realise how Comprehensive schools are organised. So I'll try and explain in as few words as possible.
Each class has a Form Tutor- and is a mixed ability group. They normally meet for registration ,messages about the school day, assembly once a week- with their Form Tutor who has overall responsibility for all the children in that class. Then the students go to lessons- in different classes, according to ability/level/special requirements. Let's say lesson one is 'maths'- some of the students willl go to Set 1, some to Set 2, some to Set 3, some to SEN support (names for Sets will change, but basically different ability groups) - then lesson 2 is (say) French- and some of the students in Set 1 for maths will also be in Set 1 for F, bus some will be in set 2, etc, and vice versa. Then if lesson 3 is PE, they will be in mixed ability groups- and for lesson 4 in Art too. But then Science for lesson 5 will also be in different groups- some will be in Set 1, or Set 3- for all those setted subjects- but others will be in Set 1 for 1 subject, Set 2 for another, Set 3 for yet another. And changes can be made throughtout the year if necessary- if a student improves, or onthe other hand falls back. There are however limitations due to class size. If you have classes of 32- how do you ensure smaller classes for groups who have difficulties? It is neither safe, nor physically or educationally possible!
If Set 1 is 35 - in sciences- it becomes positively dangerous - and in languages impossible! If 2 or 3 students improve during the year and would deserve a chance in Set 1- can you then add them to a class of 35 - no you can't. So the system is perfect for all- but funding doesn't allow it to work as it should or could.