* Religious Observances: Historically, many societies had a weekly day of rest, often associated with religious observances (like the Sabbath). This usually fell on a weekend.
* Agricultural Roots: Before widespread industrialization, many families, especially in rural areas, needed children's help with farm work. A weekend break allowed for this participation.
* Work Week Evolution: The traditional five-day work week emerged in various parts of the world over time, and the education system adapted to this structure, creating a consistent schedule for students and teachers, typically mirroring the work week structure of their parents. The weekend's religious and agricultural roots were already in place, solidifying the Friday-Sunday off pattern.
In short, it wasn't a deliberate decision to make Friday a day off, but rather an alignment with existing societal and religious norms that gradually became standardized as the work week and school week evolved alongside one another. Some countries or regions may have different schedules, but the five-day school week with Friday off is the most common pattern globally.