You should definitely talk to your teacher about this, not the internets, she/he will be able to you far more accurate comments in what the assessors were looking for in that SAC.
Additionally, your essay does read as though it has been memorised. And even though it isn't a personal essay, they were probably looking for clues that the topic was something that you considered about very closely. If you're writing from your true opinions, it reads differently than if you've memorised a big lump of text. Again, I'm not sure what the criteria were so I can't comment on that aspect much further.
As for your vocabulary, I rarely found it a problem I don't think the language you use is troubling in the slightest (I may not be the best person to ask though, I was only just reading Bourdieu this morning...). I do think though you seem to pay more attention to expression than to structure. For instance, I don't think you clearly engage with the question in your first paragraph, which is a no-no. You come very close to answering it, but just reading that paragraph, I don't really have any idea about what you think on being different entailing a struggle to belong. In the second paragraph you do refer to struggle and answer the question, but it's not clear what you mean by 'struggle' and I think you do have a problem here in relating all of your points to the concept of 'struggle' in a way where the relationship between difference and struggle is very explicit. That said, you do a wonderful job of exploring what it means to 'be different' which shows that you are capable of more fully developing your discussion on struggle.