I agree with the other reviewers that Vanessa Redgrave's performance is the highlight of the film. She plays Jean so perfectly that you can imagine that they plucked the character out of real life and simply filmed her in her natural environs. You won't find any performance by an American star---and I include De Niro, Pacino and the other top Americans of the last 50 years---which is as natural, unaffected and moving at Redgrave's. The other real delight is watching Joely Richardson play the young Jean. She looks like her mother, and she foreshadows the later development of Jean perfectly. The actor who plays Jim is perfect in that small role: handsome, not too bright, very honest and devoted. The next great performance is in the character of John Morgan, perfectly portrayed as a young man who is mentally ill, but not to the extent this is noticed, or dealt with at school. He is intelligent, but unable to relate to people as more than objects, or objectified ideals. As a character, he is creepy in just the right degree---subtly, so that the pieces only fit together later.
I'm not sure how to interpret the events which unfold or are revealed in the last 20 minutes of the film, but however you look at it, this is a depressing, very British outlook on middle age. A kind of, yes life is really awful, but we're here and the worst is behind us. In mood and final resolution, as well as in having a teacher as the central character, this movie has echoes of Michael Redgrave's very fine movie, The Browning Version.
Finally, I don't see any significance to politics in this movie. The film is a story of character development and revelation. Don't watch this movie if you are easily bored, or easily depressed, for that matter. Watch it if you want to see some really fine acting, and want to be provoked a bit.
