It is possible that they transferred from a Muggle school.
In 1890, a student was given a late acceptance into Hogwarts School of Witchcraft and Wizardry as a result of their unique ability to master ancient magic.In the 1880s or 1890s, Natsai Onai transferred from Uagadou to Hogwarts when her mother took up a role as professor of Divination.
