The prep year replaced preschool, and the age cut offs are new. prior to the introduction of the prep year, if your child was turning 6 in the year they started grade 1 - even if that was the 31 Dec then they could start school. By introducing the 30 June cut off it decreases the chances of a child born in the later half of the year repeating grade 1. and also means that kids finishing year 12 will be 17 when they finish school.

Only you can know if your child is ready for school. pre-prep and prep are good opportunities for kids to develop social skills and peer relationships. if the prep teacher your child ends up with is doing their job - if they think your child isn't ready to move onto school, then they will recommend that they repeat prep.

HTH. but as others have said, check out the qld education website, or give them a ring.