primary school, junior high school (or secondary school), high school, higher education, and postgraduate education. Structure of the basic education system In Mexico, basic education is normally divided in three steps: primary school (primaria), comprising grades 1–6; junior high school (secundaria), comprising grades 7–9; and high school (preparatoria), comprising grades 10–12. Depending on definitions, primary education comprises primaria and secundaria, which are compulsory by law, while secondary education only includes preparatoria, which has recently been made compulsory. Primary school The terms "Primary School" or "Elementary School" usually corresponds to primaria, comprising grades 1–6, when the students are 6 to 12 years old. It starts the basic compulsory education system. These are the first years of schooling. Depending on the school, bilingual education may be offered from the beginning, where half the day instruction is in Spanish, and the rest is in another language. Junior high school The terms "Junior High School" or "Middle School" usually correspond to secundaria, comprising grades 7–9 when the student's age is 12 to 15 years old. It is part of the basic compulsory education system, following primary school and coming before "high school" (preparatoria). At this level, more specialized subjects may be taught such as Physics, Chemistry, and World History. There is also the técnica which provides vocational training, and the telesecundaria which provides distance learning. Despite the similarities of the words "Secondary school" and secundaria, in Mexico the former is usually translated to preparatoria, while in other countries, such as Puerto Rico, or within the Spanish-speaking populations of the United States, the term secundaria refers to university. High school The terms "High School" usually corresponds to preparatoria or bachillerato, and follow "secundaria" comprising grades 10–12, when the student's age is 15 to 18 years old. Students may choose between two main kinds of high school programs: The SEP incorporated, and a University Incorporated one, depending on the state. Other minority of programs are available only for private schools, such as the International Baccalaureate which carries a completely different system. Nevertheless, in order to be taught, it must include a national subject at least. In addition, there are programs such as tecnología and comercio that prepare students for a particular vocational career. Preparatoria traditionally consists of three years of education, divided into six semesters, with the first semesters having a common curriculum, and the latter ones allowing some degree of specialization, either in physical sciences