year0
We were in the same position as you at the end of last year with my dd. She turned 5 in November and was third youngest in her pre-primary class. (Our school year runs Feb-Dec; it was based on Jan-Dec birthdates, ie the year you turn 4 you go to kindy, 5 is pre-primary and 6 is year one. They have just changed this to a Jul-Jun birthday system - confusing I know. Basically my dd just missed out on this change of rules, or she would have been in kindy last year and not pre-primary and none of this would have happened!)
She lacks social maturity compared to her classmates and also has some gross and fine motor skills delay (she can't hop very well, can't skip at all, can't catch a ball or bounce a ball, has difficulty with balance and climbing, finds writing difficult.) After discussion with her teacher we decided to have her assessed by the school psychologist, who recommended she continue pre-primary this year. She didn't feel she would cope with Year 1 and that it would be more damaging to her self-esteem if she had to struggle compared to her classmates, rather than simply having to make new friends in a new class. We had her privately assessed just for our own peace of mind and she agreed that she was definitely not ready for Yr 1. So we were happy to make the decision, and actually feel relieved that we are aware of her situation and areas of difficulty so we can help her now rather than finding out later when it is worse. She is now going to Gymbaroo (like Tumbletots I imagine) and dance lessons.
So my dd is back to school today with the same teacher (that was the more difficult decision! The new pre-primary teacher was a graduate so we thought she would be better off with someone who knows her strengths and weaknesses and who she already has a rapport with) and she seems quite happy about it. Further down the track I don't think she will even think about it.
I would much rather she was one of the older kids in the class feeling good about herself, than being "the little one" who always has to struggle to keep up (that was me as a student, btw!) I think repeating at this age has to be a lot better than repeating later in primary school when peer pressure and teasing would be so much more likely.
So go with your instincts; if there is any doubt that he will cope, don't force him thru the system. Speak to his teacher and with the principal, the school psych if you have one. Or have him assessed privately if you are uncertain. Good luck, I know you will make the best decision!