The large American comprehensive high school was a type of education that was developed in the early 1900s And really took off after World War II.
The idea was to have one place to educate kids of all different classes; you would bring your college bound kids together with your vocational education kids and I’ll be educated in the same institution.
This type of schooling required buses cars and cheap gas to get kids to and from the regional high schools. In the US we had cheap gas so that wasn’t a problem. The larger your school, the better your football team probably would be, so towns were happy to have larger and larger schools.
https://www.edweek.org/leadership/opinion-is-the-comprehensive-high-school-doomed/2004/09