It is not uncommon for the lord to send his archangels on quests to carry out his divine plan and protect his people. However sending an archangel like Michael to disguise himself as a human being and assume a role as a boarding school teacher was very strange. Micheal was told by the lord that the Olympians were stirring and a demigod that would be the key to everything would be there.
God was vague and mysterious as he was to all the angels except Metatron. However, if God had a specific purpose for Michael he had to carry it out as effectively as possible. He arrived at Yancy academy a school for rich and troubled youths in search of a child of a god.