My husband went to boarding school aged 8, and he loved it. He says it was the best thing for him and did no damage, but made him the happy resilient, successful person he is.
I disagree with him and think the damage it did is something he can't see, because of the damage it did.
His response to unhappiness, guilty feelings, things that are wrong or sad is: denial, humour, defensiveness. He doesn't see or admit to problems, doesn't see or admit to doing wrong, doesn't see or admit to the pain he causes other people. I think this is because he never had a safe loving place to say that he felt unhappy, lonely, or regretful. He learned, at 8, that he had to cope with these emotions on his own or risk being chivvied, teased, misunderstood, etc. As a result he still deals with difficult feelings like an 8 year old, in my opinion.
Probably this is simplistic, and only part of the truth.
My husband not only doesn't agree that boarding school might have had some impact on his emotional development, he thinks the whole idea that childhood and upbringing potentially has this sort of an effect on people is silly and self indulgent (though he probably wouldn't phrase it like that).
To himself and to the world he looks happy, positive, cheerful, dedicated, and brilliant at what he does, but to me he seems deeply damaged, and he damages the people closest to him.