I’ve seen this from both perspectives as a secondary teacher…
I can absolutely tell the student whose birthday is August 31st in their year because they are almost always the most immature in terms of silly behaviour/socialising/friendship dramas etc. Occasionally academically they stand out but not always.
HOWEVER, you are not solving a ‘problem’ for your child by deferring them, you are just presenting them with a new set of hurdles to overcome. The (extremely few!) students who are in a deferred year stand out, not because they are academically able or more able, but because they are usually miles apart in terms of interests, sporting abilities, or just general social elements… students always have a funny ability to compare ages, birthdays, who is turning teenager first… those who are deferred feel left out and slightly ostracised. There then comes teasing unfortunately.
I don’t think deferring solves anything, just creates new challenges to overcome. In my experience students who are August born, by the end of Secondary, have grown up enough alongside their peers and ‘grow up’ at the right point. Those who defer, struggle because whilst their year group turn 16, they are looking at 17 and learning to drive…. But can compare this with none of their school year peers? That’s tough. I would’ve hated to be 18 and going out for a drink… with nobody from my school year.
These decisions need to be made with the child’s entire school years considered (4-16/18) rather than just Reception year.