I think the concept of A-Level homework is different from the GCSE kind.
GCSE teacher: "Do this rather pointless sheet by the end of next week, or you'll get detention."
A-Level teacher: "I suggest you do these basic core knowledge sheets for next lesson (two days away), alongside further reading and note compiling, and perhaps an essay too please."
I've always done my homework, and have been more inclined to getting it done ASAP during my A Levels, as you'll fall behind easily and by exam time you won't have a clue what's going on.
So no, you don't have to do your homework, your teacher might be annoyed but they cannot do much since its your choice to be there.