fakerz, I think they'll sit for the AS and A2 papers all at one shot, it is possible.
Eg: Register with the board in January, complete the exams in June.

6 months is definitely a super short duration of time,whoa. O.O
TS, is there a max. number of subjects the students are allowed to take then?

Just for curiosity's sake, no attack meant =)

It's not the scheduling conflict that poses the problem here. Squeezing say...4 subjects into six months takes a LOT of dedication and hard work-it's compressing what basically is a 2 year course into 1/4th of the time recommended. Personally, I'd prefer to pace myself but if some are willing to make it at breakneck speed,why not? *shrugs*