Organized education

Before the invention of this technology, education in all types of things, including the most common magic and medicine, was based on the "mentor - students" way of teaching. One would give their students as much knowledge as they have, and people did not have much choice nearby. It was further worsened by the fact that the best specialists have always lived in big cities and rarely cared for anyone but themselves.
Students had to do everything their mentor asks for, spending most of the time doing dirty jobs and not educating, and would often mature by the moment they graduate. The system undoubtedly favoured the rich who could afford to travel far and live in expensive places with the best mentors and would often pay extra money to avoid the job of a servant.
The only exception in some cultures were clerics and paladins who would usually be given education in major temples under several teachers. Still, they were mainly educated by their primary mentor, and common people could only choose from the places they could get to.
The next step forward was taken when black orcs arrived on the Great Plains and established their city-state, Blomond. In their culture, there would be several so-called Covenants, groups of mages united by similar ideas.
Traditionally, adults would recommend their kids to a Covenant, but anyone could try to join after getting an invitation from one of Covenant's members. Rarely would a Covenant reject the recommended student, and they would all teach them together, each giving their best knowledge. Once graduated, a former student could either stay at the same Covenant, if their ideas fit him, or ask for membership in a different one.
It was also not a rare thing for a student to change the Covenant they were studying in for the sake of ideas or new knowledge, and some would even do that several times during their education. However, it was ill-perceived by some adults, especially during the later years of education. And even though changing the Covenant afterwards was a possibility, most of the students never did it. Anyway, this system offered a much more focused and versatile education and was also easier to access, even from other countries.
The next major step was taken when an Imperial Academy was founded by humans on the other side of the Krisna. Not knowing anything about the black orcs and their system, Emperor Jaymond the Wise came up with an idea of one place uniting all the best minds of his realm and accepting students from all around the country.
The Imperial Academy was state-funded and would send its representatives every year to conduct tests in all major cities. Afterwards, the results of all tests would be analysed in the Academy, and the best resulting applicants would be invited to become students of the Imperial Academy. The time there was heavily loaded in terms of both education and, once a student gets enough knowledge, science. They were taught by a wide range of professors and had access to all kinds of books in the Academy's library.
The education cost was either the astronomical amount of money or twenty years of service decided by the empire's officials. Most of the people, including many members of the nobility, chose the latter. Ultimately, the system created a firm foundation for the Human Empire in the form of numerous highly educated and loyal specialists.