Our provincial laws don't allow red-shirting. If you want to hold your child out of school until they turn 6, that is fine. However, at 6 they will go into Grade 1. Here, JK starts the calendar year you turn 4 and SK the calendar year you turn 5.
I have a child with a late birthday (within 3 weeks of the cutoff) and I was very stressed about sending him to school. Truth is that he had a hard first year, not academically but socially. He is now in Grade 1 and doing excellently.