Difficult to say, if your Biology and Dance results were the other way around there wouldn't be a slight problem. If you really want to go for it, then do so, but, in my experience, teachers (and staff in school in general) seem to be very out of touch with Oxbridge admissions (even staff which are supposedly 'experts' in it). So I wouldn't really read too much into your head of year suggesting you apply; but, of course, if you do want to, you should.