I used to go to DC and I highly doubt that either DC or ASD will take you whilst you are failing subjects. They have such huge waiting lists that you will need to work really hard to get your grades up to be accepted in the school. What year are you in?

I know it's nothing to do with your grades but the fees are very high in these schools as well. If you want them to be paid you need to prove that you're willing to work hard to get good grades.

Nationality has nothing to do with it. See if you can get a tutor to help bring your grades up so you can apply to DC and ASD.

DC is a very good school but it still won't be easy to get good grades. They are tough with their work load!! And there will still be teachers you won't like!