Should I drop photography?

I am in year 12 and currently taking English Literature, Sociology, Art and Photography at A Level.
However, since English clashes with photography I have to take photography outside school hours therefore I don't have proper lessons and I am behind the theory and practicals.
I want to take an illustration course in university and I was wondering if I should drop photography as it would affect my other 3 a levels and maybe my chances at getting into a university.

Edit: None of them are AS levels so I can't take it for year 12 and drop it at year 13

From looking around illustration courses, I see that it's not particularly your subjects that matter, but that you have an interest in illustration etc and you usually need grades in any subject (e.g. BBB) and that apart from this, it's your portfolio that forms the main part of your application. So if your grades are going to be impacted then maybe it is worth dropping photography. My only concern would be whether studying photography helps you to build up your portfolio but I'm sure you can have a photography element to it without studying it.

If you're interested in illustration, you should SERIOUSLY consider an art foundation year; there are lots. You will actually do a "rotation" in illustration in this (well, at most; since this is your end goal you'd be certain to pick a course where you did) and most likely photography, and then you would spend the second half of the course on your "major" area, which would presumably be illustration in your case.

Regardless, even if you apply directly out of school doing photography at A-level isn't likely to improve or weaken your application outside of potentially what grade you get. Therefore, you'd probably be best to drop it. There's nothing to say you can't use any work you've done so far in your portfolio, and it may be an experience you can talk about in an interview (if you can spin it positively about what you learned that you don't want to pursue and what skills you developed that you can translate otherwise).