* Ancient Greece: Philosophers like Socrates, Plato, and Aristotle had students, but these were more like apprenticeships or private tutoring than formal schools as we know them.
* Ancient Rome: More structured education existed, particularly for the elite, but it still lacked the widespread, standardized system we have today.
* Ancient China: Confucian academies provided education, but again, not in the same way as modern schools.
The concept of mass education, with standardized curricula and public schools for all children, is a relatively recent development, emerging significantly in the 19th and 20th centuries. Different countries adopted this model at different times.
Therefore, there's no single answer to when "schools" were invented. It's a continuous evolution rather than a singular invention.