I think it depends upon the school system in the United States [1]. I was with the same group of friends starting with the 5th grade (9-10 years old) through 1

I think it depends upon the school system in the United States [1]. I was with the same group of friends starting with the 5th grade (9-10 years old) through 12th grade (18 years old, last grade before college). It just so happened that not only did all my friends live in the same school district [2] but also in the same school boundary [3]. And the high school I attended was quite large (nearly 2,000 students; 450 in my graduating class alone). [1] Most school systems in the United States are vary by county to county. There's some oversight at the state and federal levels, but the higher up the government, the less oversight, generally speaking. [2] I think it was the 3rd largest in the country. Large enough to be split administratively into three sub-districts. [3] I was supposed to attend a different high school from my friends because of where I lived at the time, but the boundaries for high school shifted and I ended up attending the same high school as the rest of my friends. Strange now that I think about it, because of the three high schools in the area, it was the furthest one.