hi there
i recommend doing some online research on what age to send kids to school and then make up your own mind on what you feel comfortable with... my dd is march 24 and after alot of consideration we are choosing to wait and send her the year after... nearly everyone i know is doing the same with their kids too, however i have two good friends with kids the same age who are sending them... its entirely a personal decision but the studies are showing that having an extra year to mature and develop and play without pressures of school etc is very beneficial.... the recommendation now is to hold off on sending them if you have a child with a birthday in the first few months of the year.... it isn't necessarily about whether they are 'ready' to go or not, it is more down the track when they are older how they will deal with peer pressure etc... apparently an extra year of maturity is beneficial.... anyways there is heaps of literature online on this topic...
i will also add that australia has one of the YOUNGEST school starting ages in the world, and many countries in europe don't start their kids until they are 7.... there are lots of other activities like swimming, kinder gym, dancing, playgroup etc etc that can give them a variety of social environments that is more than adequate for their age...

anyways i am sure you can tell where i stand on the subject from this post but it really is a personal decision and there is no right or wrong as such, just different paths your child can take. i had my dd enrolled to start kinder next year but then took her name off the list. the fact that she would be one of the absolute youngest kids with other kids being up to 15 months older than her did not sit well with me... she would be 11 going to highschool with girls 13 years old, its a huge age difference....

anyways good luck with whatever you choose! i have spent hours agonising over the same thing.