Rowling wrote a series of essays, originally appearing on Pottermore, about various wizarding schools throughout the world. Aside from Hogwarts and Ilvermorny, which received extensive extra treatment, the essays described schools in Europe, Asia, Africa, and South America. The introduction mentioned that there are eleven main magic schools in the world, but the essays do not describe all of them — with Hogwarts and Ilvermorny, we only know of eight such schools. Hopefully information about the other three will be revealed at some point.
The school in Russia, Koldovstoretz Wizarding School, was not included in these essays.
Interesting facts and notes
Rowling wrote these essays in advance of the release of the first Fantastic Beasts film, along with essays about magic in North America. Since that time, no further essays have been published.