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You may not have seen it but you know the script: naive but enthusiastic teacher takes on a job in grim inner-city gang-ridden hell-hole and wins her charges over with the power of commitment and the ability to see their true potential. Meets the usual resistance from cynical establishment. 'Based on a true story', yet almost completely unbelievable. You know the sort of thing.
Now I've discussed this before but neglected to mention an absolutely crucial ingredient to this genre: ever noticed these teachers only ever seem to have one class?