Ah, var
It's absolutely amazing to see her so happy and in her words with friends who are the same
She doesn't feel weird anymore and if she is weird then her friends are too, is her attitude. 
Will have to answer busy work again, as not sure what you mean? And the mastery question 
No, it has never been a nuisance but such hard work until September.
We even took her out of school for a while as she didn't have the time to practice as much as she wanted to. Our lives revolved around her insatiable need for music. It's hard to take a back seat now and let them get on with it, you need 100% trust in the teachers.
Until the levels disappeared recently they did, however her English teacher mentioned the GCSE levels of 1-9 which I'm ashamed I didn't listen to, because dd is y7.
Most of her day is outside the nc, but all school work follows nc, they even do ks3 music which dd finds funny.
They split the year group for Humanities but for Science Maths and English they are taught together, the teacher differentiating. I'm not sure how much, but will ask for you. 
There are those who are gifted, bright, above average, average, below average and very below average in all subjects except music.
There are 22 children in her year group, only 290 something in the school.
No concept of nerds, because of course they all share the same gift in music, although obviously some are more advanced than others.
They are told from the off that they will meet people better than them, which is important if they have stood alone until joining the school.
Academic achievement and especially effort is valued immensely and any child (like mine was) not putting in the effort and you are informed immediately and we have a live stream to their time table and their live stream. There is no escape 
We have parents evening every term and you can take as long as you want with each teacher.
I'm not sure what isn't valued tbh. I suppose meanness is one, my dd not good at Maths but her teacher is brilliant. A boy chirped up that dd will never be any good at maths and she had him immediately.
She has gone from hating Maths and her teacher to actively seeking help with her prep and understanding of the work, doing the work and actually handing it in. A huge development for dd, believe me.
I read these threads with such interest and feel so sorry that many other children can't experience such a school for other subjects.
I don't know why this is the case.
I would be more than happy to answer any questions anybody has.
It's a fantastic school, not without it's problems like any other school.
But what is interesting is it stands alone and works terrifically well for the dc who attend.
It can be very stressful at times and maybe wouldn't suit the anxious or stressed child, who wasn't confident with their gift/talent/ability.
Mine fits though as she is so laid back, she's almost horizontal. I know they will get her through a few GCSE's even if it's kicking and screaming.