I can’t talk about Marlborough but know that boarding in the sixth form can be enjoyable and successful - in short, the right decision in every way and a great experience. It can be great with the opportunity to do and experience new things, make new friends and have new opportunities. But you have to recognise and be up for the following:
The DC has to positively want the experience. Understanding that means the wrench of leaving behind a school they probably know really well, school friends they feel comfortable with. Understanding that it is going to be different, unfamiliar at first and that there will probably be lumps along the way.
Accepting that they will make friends but that making real friends that you feel comfortable with takes a little time (weeks rather than a few days) however friendly and willing to make friends everyone might be.
Being willing to embrace new teachers, new ways of learning and working and understanding that some of this is the natural jump up to A levels as opposed to doing GCSEs.
Actually all of these points make it a really useful transition to university so the ‘pain’/inconvenience can be viewed as an investment or useful preparation.
With any boarding school you really need to find the one that suits you and you feel comfortable with. We found that the following to be very important:
A school which is convenient to an interesting, safe town/small city - sixth formers get visiting/going out privileges and those aren’t much fun if there isn’t any place to go. It is part of their transition to independence and adulthood plus keeping them from being bored in house. Ideally within walking distance.
A school which has dedicated houses for new sixth formers or at least a clear cohort of sixth form joiners. That can depend on the school set up but you don’t want a situation where your DC is the only newbie in a house. That would make it more isolating and difficult I think.
As for nurturing, that is going to be in the feeling you get from the school itself. I am very grateful that we not only chose a school which is pretty caring and sensible anyway but also had a housemistress who was exactly the type of sensible, caring and proportionate person who was respected and liked by girls and parents alike.
Good luck and hope it all goes well.