What was the primary purpose of secondary school before 20th century?

Before the 20th century, the primary purpose of secondary school (or what we might call grammar schools, academies, or other similar institutions) was to prepare students for university or higher education, and by extension, for professions requiring advanced learning like the clergy, law, medicine, or the civil service. It wasn't universally accessible; it was primarily for the elite and wealthy, those who could afford the tuition and whose families saw the value in such advanced learning for their sons (girls' access was significantly more limited). Practical vocational training was largely absent from the curriculum; the focus was heavily on classical subjects like Latin, Greek, mathematics, and rhetoric.