Pre-Kindergarten (not all Americans attend this): 3-5 years old
Kindergarten: 4-6 years old
Elementary school is 1st-5th grade.
1st grade: 5-7 years old
…
3rd grade: 8-10 years old
…
‘Middle School’ or 'Junior high is 6th-8th grade.
6th usually is 11-13 years old
and High school is 9th-12th grade.
we typically end with 12th grade at 17-18 years old
These are general ranges as it does vary from state to state with allowances for birthdays and advanced placement (i.e. in many places you can test out of or into various grades), but the general idea is (except pre-K) you spend 12 years between 5 years old to 17 years old in grades 1-12. That plus kindergarten are all that’s fully paid for as far as public education goes.
Second question, what’s “third grade” for you?
In france it’s like 15-16 (they count backwards too so second comes after third), in Sweden it’s like 9-10.
In the US grades are (usually) the following:
Pre-Kindergarten (not all Americans attend this): 3-5 years old Kindergarten: 4-6 years old Elementary school is 1st-5th grade. 1st grade: 5-7 years old … 3rd grade: 8-10 years old … ‘Middle School’ or 'Junior high is 6th-8th grade. 6th usually is 11-13 years old and High school is 9th-12th grade. we typically end with 12th grade at 17-18 years old
These are general ranges as it does vary from state to state with allowances for birthdays and advanced placement (i.e. in many places you can test out of or into various grades), but the general idea is (except pre-K) you spend 12 years between 5 years old to 17 years old in grades 1-12. That plus kindergarten are all that’s fully paid for as far as public education goes.