I wouldn't dismiss it out of hand if a) your daughter wanted to go b) it is a good school and c) it is a good fit for your daughter.
My Year 9 daughter is at a specialist dance/stage school where most board. We live close enough for her to commute which is just as well as she would not suit boarding at all. But, had she been a different type of child, I would have happily considered boarding at 13. Possibly at 11 too, though not younger than that.
I am also a boarding tutor in the private prep school where I teach. We have around 30 full boarders between 7 and 13, another 20 or so weekly boarders and about 60 who do either 1, 2 or 3 nights a week. The vast majority of the regular boarders are 10+ but there are always exceptions who either want to or need to board. Generally, they children are very happy. I'm sure many would be happier at home though.
I don't think children suffer at boarding school nowadays. Any good school would point out to parents if a child was consistently unhappy and suggest they leave/go day.
However, I do think it's a case of some thrive but some just survive.
You need to know which it would be for your daughter.
I think the eating disorder line that is always, always brought up on this thread is a bit of a myth though. Astounded at the poster who has found that 90% of the boarding school educated people she knows are/have been eating disordered.
I know about 150 people with an eating disorder (because I have anorexia, not because have some kind of weird obsession!). About 15 went to private school, of whom about half boarded. That's fairly consistent with any group of 150 people I think. I went to a comprehensive. The one child at the private school I'm teaching in now with a potential eating disorder is a day pupil. Any issue with any of our boarders would be so, so easy to spot.