Public schools in nSW will be getting smaller classes as the grades go on as part of their new policies, it also depends on how close they are to getting an extra teacher. This year we qualified for 16 teachers by about 5 kids so all our class sizes are quite good (DD has 25 in her Yr 4 class) had we not got those extra 5 kids we would have had only 15 classes which meant the primary classes would have been considerably bigger.
Unless it is a private school they cannot guarantee class sizes in primary.
BTW Marydean - brilliant point.