I think like any of these things it will depend what you’re coming from and what your expectation is.
don’t have any knowledge of ncc except that dd’s friend who is in it is applying for conservatoire and already has offers for voice so is obviously taking it seriously.
dd2 is in nycgb though and has been for several years. I was a bit sad to read that someone had been bored and found the sightreading standard ‘pitiful’.
For dd 2 nycgb was transformative. She has always loved to sing and got into the girls choir from a state school where there was virtually no music. The courses were wildly exciting for her- like a visit to a different world.
nycgb courses gave her her confidence to walk into rooms that would have been alien to her before. Without these courses, which taught her to love collaborative music at a new level she would never have walked into a specialist school and felt she had the right to audition- although she is a first study instrumentalist not a singer. She also learned she could find people ‘like her’ among musicians.
Now of course she has much more music at school - lucky girl- she finds on the courses that there are some people whose sightreading is less good than hers.
nycgb takes children with excellent voices who may not be as lucky with training as those who might be in a choir school or similar. So there will be more of a range in terms of this.
Dd does now have grade 8 singing (along with diplomas on two instruments) but still loves the courses and the sound made by this choir and the fun they have learning the pieces on the courses and just hanging out together making music.