There are six witcher schools mentioned in the various adaptations of the Witcher saga. Three are mentioned in the graphic novel, Zdrada, fourth appears in the The Witcher 2, fifth in The Witcher 3 and sixth in its expansion called Blood and Wine:
Witcher Schools are the training ground for itinerent monster slayers to-be, each one is built on the blood, sweat, and tears of countless children who stood within them, honing their technique and skill. Though each school trains in the ways of weaponry, alchemy, and the beastiary, each school trains in arts and equipment that are unique to them. Such as the School of the Cat that designs armor that provides maximum flexibility, or the School of the Manticore that studies the art of poisons, or the School of the Griffin that emphasizes magic.