system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why does the US have a 3 school system (elementary, middle, high)?
gpt
Government operated schools in the USA often went until around age fourteen with the expectation that students would then enter into apprenticeships or work in the family business.

As the economy changed, more parents wanted their children to be eligible for office employment. At the time, office workers came from the educated elite who attended preparatory schools. The government-operated high school was an attempt to emulate this.

At the same time, many school populations were rising, requiring the building of more facilities. Some suggested that, instead of just building more elementary schools, the existing schools could have their age range reduced and a new facility could be built for early-pubescent students which would act as a bridge between the elementary system and the high school system. This would be called a junior high school and later a middle school.