My DS in p3 (just turned 7) is the youngest boy in his class with an end October birthday. In his school there is a practice of holding December to February birthday back a year.
We did think about it before he started school but was assured he was ready etc....
He is struggling with the speed of work ( he is a leftie and hates writing) and is in the lowest group for reading ( ort 9 which he is managing but doesn't find easy). He is also lacking in confidence, saying he is "rubbish".
Socially he is fine although quiet as there are some big characters in the class that tend to take over. He doesn't have a best friend but is friendly with most and is popular.
Next year is a big step up in his school as it is a private school that has a prep school system from age 8. More responsibility, longer days, games 3 afternoons etc... Also a different part of the school and playground.
Further up the school new intakes seem to be old for the year ( almost a year older than he would be).
All this is leading me to think he may in the long turn be best repeating this year rather than waiting until further down the line.
if he were starting school, I'd say an October baby (usually only January and February birthdays and a few December and even fewer November) was "early" to defer - but it is possible. If he were at a state school, he'd now need to get an Educational Psychologist to approve him repeating a year - but at least at a private school you have more flexibility.
You know your son and the school best. If you feel he's be better repeating a year, he'd be best doing it sooner rather than later. What does your gut say?