I would definitely say write about YOU and your own life - i'm sure your first excuse is nothing happens in your life, but think outside the box and you will come up with a good idea!
I would say just lock yourself in a room, grab yourself a piece of paper and then start writing about anything even if you think the story won't go anywhere. Then come back the next day and read over the written piece of paper and this should trigger a story in your mind which you can work with. Remember I'd say most of the marks in your creative comes from unique and original ideas more than how literate you are. As a suggestion, try these ideas (again, this may be cliched but if you can give it a good twist it WILL work):
-Migrating from another country --> belonging or not dis-belonging in the new country
-A person getting fired from work
-A person revisiting an old home
Big DON'Ts:
-Stay away from anything school related (i.e. schoolies, new student at school)
-Violence, drugs, crime, sex etc.
-Death (unless it is done in an appropriate manner)
-Waking up from dreams
-Fantasy, science fiction (don't think its worth the words to spend describing elaborate settings)
And remember your creative writing only needs to be around 800-900 words which allows some time for adapting