If she is only 4.5 - I wouldn't send her. She will be one of the youngest in her year. The teacher/student ratio is much bigger at school and the level of support and supervision is very different from Preschool/Kindy - kids need to be more independent and resilient) I wouldn't see it as "repeating" her or holding her back. Being at least 5 is the generally norm for the first year of formal schooling these days. So it would be essentially sending her early at under 5. My DS1 is 4.5 and none of the 10 kids from our mothers group (birthdays April to July - our cutoff is 31 July in NSW) are going to school this year. Some are "academically" ready or "socially" ready but school is full on and we all felt giving our kids another year was of the greatest benefit.