At first, it was believed [by whom?] that teaching modern languages was not useful for the development of mental discipline and so they were left out of the curriculum.[citation needed] When modern languages began to appear in school curricula in the 19th century, teachers taught them with the same grammar–translation method as was used for Classical Latin and Greek.[3] Textbooks were therefore essentially copied for the modern language classroom. In the United States, the basic foundations of the method were used in most high school and college foreign language classrooms.