The detailed curriculum in each school level, the general objectives of each subject, and aims and contents of each school year for each subject are precisely controlled by the National Course of Study. It may seem that the national government limits and controls the contents of education and its teaching methods; however, the Course of Study only presents the frame structure of the teaching and the classroom teacher has the liberty of the details presented. The Course of Study is revised once every decade or so. [Source: Yoshiro Hatano, Ph.D. and Tsuguo Shimazaki Encyclopedia of Sexuality, 1997 hu-berlin.de/sexology ++]