From family/friends experience, in Vic it depends on the suburb. Most schools in my area would prefer a child to repeat kinda (at the parents expense, no governement funding) than repeat prep or grade one, this is for social reasons not acaedemic.. infact I know of one school where if a child needs to repeat prep they have to go to a different school for a year then come back.. stupid in my opinion but their rules. You can hold your child back a year but you have to pay for the kinda/pre-school the following year as there is no government subsidy.
I know different states have different rules.
Then there is the other side of the equation, kids getting promoted to the next year for social reasons not acaedemic like my xss... he repeated kinda so is 1 year older than most, he is going into grade 2 next year and has barely reached the prep-1 progression level, yet because of his age he has to progress for social reasons.