I don't think that boarding school is a great idea tbh. Parents are not involved in the day to day raising of their children and later congratulate themselves on the dc being so resilient, but frankly they've had to be. I don't think that's ideal.
I don't think this is really fair - DD was a weekly boarder from the age of 14 because the course she was studying (in France) was too far from home. She chose to go and she thrived. Incidentally her place was funded by the state so we are by no means "posh".
My DD has just started at university in UK - she is resilient, confident and thriving and I am very proud of her. Any suggestion that I was not involved fully in her life is insulting and implies prejudice and lack of understanding about boarding.
I did not "farm" my parenting out - I supported my DD to do something that she wanted to do at the age 14. If you think it's hard having an empty nest at 18 try it at 14 - it's not a picnic.
However I will add that her earlier independence - making friends, travelling to and from lycee (3 hours away), dealing directly with tutors etc... has made her more confident and it was something I noticed when I dropped her off last week. She was the youngest there (17) but engaged with other students and parents with confidence and was more than able to hold her own.
Whether this is just DD (she has been resilient in that we left the UK when she was 7 and DD was then educated in France - so is used to challenges) I can't say.
That said she'll still bring her washing home, texts me about how to cook simple dishes, has already asked for money (loan not in yet), took her favourite cuddly away with her and messages me and her DF most days :)