What is the main reason for why children did not go to school in the US during the 1800s?

Explanation:

It's hard to imagine, but in the 1800s a single teacher taught grades one through eight in the same room. Rural areas were just too sparsely populated to support multiple classrooms, so towns built one-room schools about 20-by-30 feet large. In the 1800s, Horace Mann of Massachusetts led the common-school movement, which advocated for local property taxes financing public schools. Mann promoted locally controlled, often one-room “common schools” in which children of all ages and classes were taught together; later he introduced the age-grading system.