Nothing wrong with YOUR answer mamya ... homonyms do not have to be spelt the same, they should have the same sound but only possibly the same spelling, with a different meaning and origin.
8 year olds shouldn't be doing homework, they should be up't chimney's or workin in't mills, or such like. Seriously thopugh is they're a word or a contraction of two words! If so it don't really matter about homophones or homonyms. By the way if I had used They're whilst at school I'd have had my knuckles severley rapped for laziness.