There might be a textbook, which the student has been forced to buy at an exorbitant price when entering the school, but damned if most of the teachers will use it. The truth of the matter is that the school wants to prevent the teacher from entering into private arrangements with the student before leaving his part-time job. Also, many schools hire teachers by the lesson or day, so chances are high that that same teacher won't be around the next week. Non-native speakers of English are often used to reduce costs. Americans, British, Australians, and Canadians are expensive.
Qualified teachers are the rarity, rather than the norm.
As such, most schools will employ one or two teachers with credentials sufficient to qualify for a work visa as a front, and hire the rest on an illegal basis. Many foreign teachers are advised to get cultural visas in order to teach by misinformed friends. However, according to the Japanese Ministry of Justice, people on cultural visas are not allowed to work in Japan. How long this will continue remains to be seen though, because the Ministry of Justice is beginning to crack down on illegal aliens. In Japan, contracts are actually stamped with a personal seal.