With the public school system here in SA and I am not sure if it is the same as all states but if your child is to attned a public school in the are you live in then he will be intitled to go there no matter when you enroll him, with my ds he has changed schoold twice and both times they enrolled him the morning that he was starting as they were public and in our area, so they can not say no kwim, wtih private or independant schools that is when you need to enroll them a year or 2 or even more thatn that earlier so they get a place.

but yeah as Danni said ring the school and find out that is the safest way to make sure you wont miss out.

HTH

Good luck