Children have to have turned 5 by end of April to start Prep. But you do have a choice to send them that year or send them the following year.

Generally overall broad band spectrum (lol) children turning 11 are in grade 5 but saying that his birthday is april he might be able to start gr6 next yr cause of when his birthday falls. It will depend on what the school you are attending to send him too says.

Have you chosen a primary school as yet? Maybe contact them (the principal)