My school is very concerned about attendance, even for sixth formers, so my attendance is 100%. Each half term they provide a list of your attendance for each day, and if there are any times you are absent - even an afternoon - they'll chase you up on it.
I could pretend to be ill, and I know some people who have gotten away with that, but my parents wouldn't like it, and it'd be a massive pain to catch up on all the work I'd missed. I'd have to find all the teachers, get the lesson work and homework, and complete it ASAP. So if I missed a day, I wouldn't actually be missing any work.
Thankfully I do get study leave as an A2 student, though it doesn't start until 28th May. As most people have at least one AS resit exam, generally before study leave, I'd prefer it to start early/mid-May.