i don't study any of them but my friends do and some have dropped from those lessons, claiming its too hard but those who did well at the subjects at GCSE did well at A levels..
if that's what you want to do, then i would say go for it, but A levels are a lot harder, keep that in mind
you have to have a real good brain and determination to do them...they are good a levels though and good luck...depending on the exam board you are with check out the specifications of the subjects to see what you'll have to do and whether you'll like doing the course.