My Son is born in 28Feb06. He is study nursery at this year. Next year september, he will be study K1. Big boy is better due to he can more understand the teacher say and teach.
While I agree with you, I wish to point out that there could exceptions. My friend's son was born in Feb 2003 but is now studying P.1 in a quite famous primary school (not an IS). That means the boy started P.1 at the age of 5 years and 6 months. Anyway, the boy, as I observe, is very smart in terms of both physical and mental performance.