I know a boy who was born in Dec, he was studying in Playgroup only at the time of interview. However, both St. Cat and Victoria accepted him last year. My baby was studying in pre-nursery class at the time of interview, we only receive either 'waiting list' letter or 'reject' letter from famous school.
My daughter didn't join any nursary classes but playgroup once a week.
If there are people who could talk care of the children, I don't think it is necessary to join the nursary. Somehow they would feel pressure from the school even there are no real exam or assignment.