With the new kinder hours, 4yr kinder is for 15 hours / week. which means that a single kinder teacher can't take 2x4yr classes.

Schools have feeder kinders, and being in the right kinder can make getting into the school you want easier. So to ensure a place for 4yr, parents enrol their kids in 3yr kinder. Then you get first option at 4yr, as do subsequent kids.

ITMS.

As for us, well, DH decided we couldn't afford CC but kinder was cheaper and it gave him the skills he needs to transition to prep OK. Plus he's in the community that he'll be in at school - a number of kids from our kinder are going to his school.