hey my school does it.. i know alot about it..
its like you have to do either 6 AS LEVELS or 3 A LEVELS in one session..
its a points system.. u get 60 points for an A in single credit (AS LEVEL) subject..
and 30 points for an A in half credit AS subject for eg; thinking skills, GP etc..
if u get total 360 points i guess its called AICE diploma with distinction and a lil less means merit and so onn..