In 1962, he was sent to another school also attended by his father - Gordonstoun - in the north-east of Scotland.
It was said that The Queen Mother, who Charles was very close to, tried to stop Queen Elizabeth II and Prince Philip from sending their son to a secondary school so far away, but his father, a tough disciplinarian, persisted because he thought he would have more privacy in such a deeply remote area.
In a letter dated May 23, 1961, The Queen Mother wrote that he would be “terribly cut off and lonely in the far north".
She added: “I suppose he will be taking his entrance exam for Eton soon. I do hope he passes because it might be the ideal school for one of his character and temperament.”
In 1966, a then 17-year-old Charles spent two terms at the Timbertop campus of Geelong Grammar School in Victoria.
He described Timbertop as the happiest time of his whole education and that love for Australia has continued throughout his whole life.
According to Vanity Fair, the prince was liberated by the informality of Australia where he quickly learned that “there is no such thing as aristocracy or anything like it.” For the first time, he was judged on “how people see you, and feel about you.” Students and masters treated him as one of them, and to his surprise he felt little homesickness.
He was mildly teased as a “Pommie”, but faced none of the hazing he did at Gordonstoun.
It was during this time in Australia that he also learned to meet and greet crowds.
"He was a friendly, intelligent, natural boy with a good sense of humor,” said Thomas Garnett, the headmaster of Timbertop, “someone who by no means has an easy task ahead of him in life.”
When he returned to Gordonstoun after his time Down Under, Charles was made Head Boy, just like his father before him, but he never warmed to the boarding school like his athletic father did, describing it as “a prison sentence” and calling the school “Colditz in kilts”. A former school friend said he was "relentlessly bullied" there.
In a letter sent home in 1963, Charles wrote: “The people in my dormitory are foul. Goodness, they are horrid. I don’t know how anybody could be so foul.”
In episode 9, season two of The Crown, it looks at the Prince's experiences at the school, focusing on his shabby dormitory, hostile classmates and freezing morning runs.
But in an Observer interview from the 70s, the Prince said: "I am glad I went to Gordonstoun. It wasn't the toughness of the place - that's all much exaggerated by report - it was the general character of the education there - Kurt Hahn's principles; an education which tried to balance the physical and mental with the emphasis on self-reliance to develop a rounded human being.
"I didn't enjoy school as much as I might have, but that was only because I'm happier at home than anywhere else."
He added that the "discipline" at the school gives "shape and form and tidiness" to life.
Despite his hardship at the Scottish school, he earned two A-levels: History (grade B) and French (grade C).
His two brothers, Prince Andrew and Prince Edward, were also sent to Gordonstoun.
He broke royal tradition again, when he went straight to university after his A-levels, rather than joining the British Armed Forces.
In October 1967, he started in Trinity College, Cambridge, where he studied anthropology, archaeology, and history.
During his second year, Charles attended the University College of Wales in Aberystwyth and studied Welsh history and language for a term.
He graduated from Cambridge with a 2:2 Bachelor of Arts on 23 June 1970, the first heir apparent to earn a university degree.
In August 1975, he was awarded a Master of Arts degree from Cambridge.