But as a Guyanese immigrant and part of an ethnic minority in London, and despite Braithwaite's succession of degrees from universities in Guyana, New York and Cambridge, where he gained a doctorate in physics, it was the only work he could get.
After initial hostilities, his new job became a life-changer, marking out a path for him as a social worker and author of note. It also gave him the material for one of the most enduring literary works of its era. Now, following an iconic swinging 1960s cinema treatment, as well as a more recent radio adaptation, that auto-biographical novel, To Sir, With Love comes to the stage in an adaptation penned by Ayub Khan Din, who made waves with the big-screen adaptation of his own semi-autobiographical play, East Is East.
Now 101, Braithwaite flew back to the UK from New York for the opening night and was impressed. The production is one of the first by recently appointed artistic director of Hull Truck Theatre Mark Babych, and co-produced with the Touring Consortium Theatre Company and the Royal and Derngate Theatre, Northampton.
"I think it is excellent," he says of the production, which features Matthew Kelly as the school's headmaster, Florian, and Royal Shakespeare Company regular Ansu Khabia as Ricky, Braithwaite's fictionalised younger self. "It was a nice experience, but I needed to be reminded of so much, which is a function of age, I suppose.
"Normally I don't think about my time in the East End, and watching the play, the events it describes all seem a bit unreal to me now. In fact, I had to strain to imagine myself in that situation."
Even so, Braithwaite's memories of his first day at the school are still vivid.
"All I remember is that it was hell," he says. "The students had decided to make it hell for me. I chanced upon education. It was like an accident that happened to me. Those kids in the East End made a great impression on me. They seemed so infused with life. I connected with them purely out of my own wish to survive. It struck me one day that the children didn't have any respect for themselves, and this was why they had no respect for other people and I seized upon that idea. I challenged them to respect themselves.
"I don't know if I changed any lives or not, but something did happen between them and me, which was quite gratifying. I did not keep in touch with my former pupils. I had gone to the school to do a particular job and I felt I had completed my work with them. However, one of the strange things about life is how often circumstances repeat themselves.
"I would be walking to work and people would come up to me and say, 'Hiya, sir!' There came a point when I was Sir to the parents as well as to their children."
Braithwaite had not planned to turn his experiences in the East End into a book. Only when he left teaching did he take stock of what had occurred.
"To help me teach I kept notes of each day's activities," he says. "Once I was ready to quit teaching I had no further use for these notes, and I had decided I would burn them when a friend suggested I write a book based on them."
Braithwaite's book was published in 1959, but for many To Sir, With Love only became known through writer/director James Clavell's 1967 big screen version, which starred Sidney Poitier. The film was a hit, partly, one suspects, because of its casting, which included Glasgow-born pop star Lulu playing a rather unlikely chirpy Cockney.
Lulu also sang the film's Don Black and Mark London penned theme song, which, while relegated to B-side status in the UK, stayed at No 1 in the Billboard Hot 100 in America for five weeks. Despite the film's iconic status, Braithwaite was less than impressed by the end result.
"I was disappointed," he says. "I was not involved in the making of the film. A man (Clavell) came and talked to me about the film rights, and I could see he was not concerned at all with my interests. He made it seem as if the book and the proposed film of it were totally separate. When Clavell wrote the screenplay, he wrote his view of the book, which was very different from mine. When I saw the film, something had been lost in the transition from book to film."
Given that one review of the time suggested the film's "sententious script sounds as if it has been written by a zealous Sunday School teacher after a particularly exhilarating boycott of South African oranges", the opinion of the book's author was clearly shared elsewhere.
With this in mind, Din and Babych's new take on To Sir, With Love is more faithful to the book's original 1940s setting, when song and dance brought some life to an otherwise austere existence. A two-part radio version by Roy Williams, starring Kwane Kwei-Armah, did likewise in 2007.
Braithwaite puts the enduring appeal of To Sir, With Love down to the simple fact "it appeals to a lot of people. They each find what they are looking for. Each person is looking for something he or she could use in their daily life."
More than half a century on from the publication of the novel, Braithwaite remains sceptical about any improvements in the education system to give opportunities for children from poor or ethnic minority backgrounds.
"I don't see much progress," he says. "I see change, but the fundamentals remain the same. When people read my book, when teachers read it, it may lead them to some self-examination. In my view, that is unfortunate. This book provides them with a moving target and the target is me as I faced the challenges in that school."
To Sir With Love, King's Theatre, Edinburgh, October 29-November 2