The film was made after the novel by
E.R. Braithwaite, which describes (presumably) his own experiences with racial and social issues in British society.
It tells the story of a highly trained and competent engineer from British Guyana who, upon arriving in England to look for a job, is astonished and appalled to find that people categorically refuse to hire him because he's black. Eventually, he takes a job as a school teacher in London's East End. The reader is amused to find that the value judgements on race the author finds so unheard of are perfectly normal to him when used on class.
In my translated copy, the original title reads: "TO SIR - WITH LOVE".