My child has just gone to boarding prep school and he absolutely loves it. He wasn’t “sent” against his will, which is perhaps different from some of the experiences on this thread, he was keen on going.
He was quite lonely before he went, being an only child of a single mother, and he wasn’t all that happy at his day school.
But now he has lots of “brothers” who between them enjoy all the same small boy things that he does, and lots of excellent older male role models at exactly the right time in his development for that kind of thing (see Steve Biddulph). He loves coming home every weekend or two for exeats and half terms AND he loves going back to school because they have so much fun.
If he is happy then I am happy, and the time we have together is so much better now because I am always completely “present” and focused on him when he is home, not trying to juggle other things. I look at some of the other parents at his old day school, who thought it was scandalous to send a child to boarding prep, and I see people who do long hours at the office and mostly delegate their children to nannies, au pairs and housekeepers, and when they DO see their children it usually features a tearful argument with an exhausted child about homework.
Some people, particularly people of my generation and older, had a miserable time at boarding school, and I know first hand how that stays with you. However times have changed, and I think it can make really good sense for some families and some children.