Something else to think about:
My DD has an end of July b-day and I sent her on time. She is by far the youngest in her class because most everyone else held their kids back if they had a summer birthday. She is 7 and there are students that turned 8 before they entered 2nd grade. She will turn 8 right before 3rd grade.
So although she is only 20 days after the cut-off, once she is in school there will be kids that will be over a year older than her and then you need to add the kids that have been held back for various reasons after they entered the school.
Just something to think about.
Definitely. My DD turned 12 last weekend. Her best friend is turning 13 today. They are both in 7th grade. There are children (mostly boys) in DD's class who will turn 14 before the year is out. People around here really believe in holding the kids back.
Now tell me that a 14 yo should be in the same class as a 12 yo. Yes, DD is academically advanced (which is why I didn't hold her back despite "expert" opinions, but I am really uncomfortable that she is not hanging out with boys who are almost 2 years older than she is.
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My DS11 is one of the youngest in his grade. (6) Most of the parents around here hold their kids (especially the boys) back and have them start kindergarten a year late. Why? Several of them have told me it was so their kids would have an edge in sports.