Hi aisling18,
It sounds like you're in the early phase of your studies. Is that true? As it's already been pointed out, the scores that you receive for the Essay and IR section of the GMAT are separate from your overall score out of 800 (which is based on your performance in the Quant and Verbal sections). While some Schools may be interested in only certain parts of your overall score report, you should still plan to properly train for everything that you'll face on Test Day - even if it's just a bit of cursory practice (it would be unfortunately if a School that you were interested in changed its policies regarding how it assesses the GMAT score - and you were rejected for not performing at a sufficient level in the areas that you 'skipped over').
I'd like to know a bit more about your timeline and goals:
1) How did you score on this CAT (including the Quant and Verbal Scaled Scores)?
2) What is your goal score?
3) When are you planning to take the GMAT?
4) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich