Generally in the US it is:
* K ~5 yo
* 1st ~6 yo
* 2nd ~7 yo
* 3rd ~8 yo
* 4th ~9 yo
* 5th ~10 yos
Give or take of course since birthdays don't align perfectly.
That seems to roughly align to US standards for the same age but not the same grade.
Generally in the US it is:
* K ~5 yo
* 1st ~6 yo
* 2nd ~7 yo
* 3rd ~8 yo
* 4th ~9 yo
* 5th ~10 yos
Give or take of course since birthdays don't align perfectly.
That seems to roughly align to US standards for the same age but not the same grade.