I picked this up second-hand after hearing something on the radio about the author (I now realise this book and the sequel were serialised on Radio 4 a few years ago). I saw the film starring Sidney Poitier many years ago so knew what it was about. In the book, as always, you get more: his background as a pilot in the RAF, and the discrimination he faced after demob which was overt and appalling.
The real story remains, however, his struggle to engage his final-year students at an East End secondary school and to try to influence their way of thinking and their behaviour. Written in a somewhat formal and dated style, it nevertheless makes a real impression and literally gets you under the skin of what it was like to be a well-educated black person in Britain in the 50s. One of the most memorable scenes in the book (which I can't remember being in the film) was a chance encounter with an elderly and wise man on a park bench who literally changed his life by showing understanding and pointing to a future career. On such unpredictable events our lives can turn!
After I had finished the book I was intrigued to know more about this writer and there is quite an extensive and informative Wikipedia entry on him. Among other facts are that both his parents went to Oxford University, he got a degree and a doctorate at Cambridge, and later went on to become Amabassador for Guyana in Venezuela. He has written several other books, and I would certainly be happy to read more by this author.