My father was shocked at the schools chosen for Prince Charles and Princess Anne, that I do remember. Not that he had any say in the matter, as an ordinary citizen, and as he had not himself been to boarding school or had ever considered sending his children away to school, you could rightly call him prejudiced.
I honestly do not think any boys' boarding school of that era would have been better.
Since the 1970's many of them not only in Britain but all over the world have been accused of ignoring sexual abuse either between masters and pupils or between older and younger pupils.
I have no idea whether sexual abuse was prevalent at Gordenstoun or not, when King Charles was there, but I do know that in my childhood and teenage years ( I am a year younger than Princess Anne so this is relevant) most middle class Scottish parents were shocked by the way the royal children were being brought up, their public behaviour, and the immorality of some of their adult relations, such as the Duke and Duchess of Hamilton, Princess Margaret and Lady Mountbatten - not so suprising Prince Andrew turned out as he did.