Can you sing that "with a little help from my friends" ..........that is?
Lets talk about the NC,
How can it widen the gap between all students taught in mainstream state? when all state schools follow the NC. Surely if schools followed their own curriculum the differences in provision would be wider, differences in subject, depth & breadth of study, differences in targets and depth of knowledge attained and differences according to the particular ideology of the school.
How does it widen the gap btw state and private? Well the NC itself doesn't. However private schools are free to follow it if they choose, some don't. Of those that don't and those that do, I think you'll find that the differences between standards and results are minimal.
The difference between private and state, is that private can, by and large choose it's intake, they can be selective. They also have smaller classes and better facilities. They can exclude pupils easily as you have made great bones to explain and they often have parents that support their children and share in the ethos of the school. There are many reasons why there are differences, but the NC is not the cause of the discrepancies.
I followed the NC and sent my HE son into secondary at 11 working btw the levels of 7a and 4a.
Whilst I think that there maybe a problem with how the levels are paced/stepped, the classes huge, the teachers stretched and resources thin on the ground, the problem isn't with the NC.