I am born in May, and in my day (lol) the cut of was June. So I started prep at 4, turning 5.

I never saw A problem with this, neither did anyone else - the cut off is the cut off!

The only time it was an issue was in high school, where I had my peer group , most of whom were older (I was the 3rd youngest in the year level) and they were as such allowed more social freedoms than my parents allowed me - parties, sleepovers, etc...I was by no means restriced or sheltered or what have you, but there were many times when I wasnt allowed to go to an event due to my age.
And then when I finished year 12, I was still 17 - didnt turn 18 til the following may - so had the same problems that Feeb referred to lol
All of which was a PITA for me at the time.

I was more than ready to go to school though, and would certainly hope that if my mum had been told what you were, then she would have sent me anyway!

I would be asking this school where the "trend" is coming from - is it a school policy? Something that they themselves endorse to institute? Or is it more a general trend in parents and parenting that she is observing and commenting on?

From the sounds of it your DD is well and truly ready to head off to school and will do very well there - I wouldn't keep Charlotte out of school for an extra year unless she was very certianly NOT ready, which would be plainly obvious.

Oh, have any other schools you've visited mentioned this 'trend'? I would ask them also when you visit.

Good luck!