"The number of countries that have their own magical school is minuscule compared to those that do not. This is because the wizarding populations of most countries choose the option of home schooling. Occasionally, too, the magical community in a given country is tiny or far-flung and correspondence courses have been found a more cost-effective means of educating the young."
Here's a bit of information about the new schools Rowling revealed:
This Brazilian school can be found hidden within the South American rainforest. To Muggles, it looks like a ruin, but for those who can see it in its full glory, the castle, carved into a golden rock, looks like a temple. Students wear bright green robes and are especially skilled in Herbology and Magizoology. Castelobruxo offers popular exchange programs for wizarding students at other schools who wish to study Latin magical creatures like flora and fauna.
Rowling released the name of this school, but held back details about its location and student body. The map on the site suggests it's on the East Coast of some country or continent. Many think it's the American school Rowling has alluded to. If so, Rowling has said the North American school is not in New York and that "indigenous magic was important in the founding of the school." She once said, "If I say which tribes, location is revealed."
This school, located in Japan, has the smallest population of students out of all 11 wizarding schools. The school is comprised of a palace called Mahoutokoro, which is made of mutton-fat jade and is situated at the peak of the volcanic island of Minami Iwo Jima. At Mahoutokoro, students receive enchanted robes when they begin their first term. The magical robes change and grow in color and length as students' grow in height and size and as their learning increases. Upon arrival, the robes are a faint pink color and they turn gold if high grades are acheived in every subject. They turn white if a witch or wizard illegally practices magic or breaks wizarding code. The school is known for having a strong and dedicated Quidditch team.
Uagadou, the largest of all wizarding schools, is one of few wizarding schools in Africa that have flourished. The only address ever given is "Mountains of the Moon," and people say the school is carved out of the side of a mountain and disguised by a mist, so it looks like it's floating in mid-air. Students who graduate from this school have particularly strong skills in Astronomy, Alchemy and Self-Transfiguration. Here, many witches and wizards conduct spells using just their pointing fingers or through hand gestures. Unlike Hogwarts, Uagadou invites young magical people to attend the school by sending Dream Messengers to children as they sleep. Selected students wake up to find a token in their hand with a special inscription.
Discover four additional wizarding schools from around the world on Pottermore: https://www.pottermore.com/writing-by-jk-rowling