Yeah it was difficult for me not to analyse it as if it were a text response. When Abraham was boarding up her window I got so caught up in saying Sannie was a saviour and it was symbolic when she put her hand over it (it looked like a crucifix) and realised it was all for nothing.
Personally I'd go for imaginative because it's what I enjoy most. However it seems like a solid essay/article prompt also. As for evidence if you were going to write an essay, I would use the scene in which Sandra is told by another girl (Emma?) that she was born in Swaziland and doesn't mind her skin colour (born in Swaziland/values/prompt) and I would juxtapose that with the other girls at the school. You could also use Abraham's fondness of the nationalist government, Pietrus' views and values and how he's been made to hate the white mentality and status via being born into an apartheid country etc.
Alternatively, you could use Sandra as evidence against the prompt, how her values have been shaped by experiences rather than society, and her beliefs couldn't match society's as that would shatter her own identity. You could also use the "Chicken guy" who doesn't mind her skin colour to go against the prompt.
As far as imaginative goes, the paper is your oyster. Depending on what form you would like to write I'm happy to bounce ideas =]