mmzz all mine have refused to do NCS. It's a big commitment timewise too. I wasn't impressed by some of the people on the phone trying to organise it either, maybe I was just unlucky, they couldn't answer any of my questions on what would happen etc or else relegated ds1 one to the extreme SEN pile when I said he had dyspraxia (oh he will need a 1:1 NOOO he won't), I wasn't able to explain that he needed to know just what was involved (ie the location!!!) before signing up. It really is a no-brainer with a child with ASD/dyspraxia that they need to know what they are being scheduled to participate in [grrrr] Anyway he refused point blank and so has ds2 now, and dd thought she couldn't face it either.
All want to get summer employment though, working for family members so that is a start.
Sixth Form ds1 had team building activities when he started Sixth form - I think they make a big effort to integrate newcomers and emphasise that the sixth form is different from the rest of the school whether it is part of a school or a college in its own right. The academic bit is the most difficult part imho, the social side seems to be so much easier than school, smaller groups, respect for hard work etc, and no cliques.