School education in Thailand is 12 years in length and free to all students in the public sector. The first nine years of schooling are compulsory. The education system has a 6-3-3 structure: six years of primary education, three years of lower secondary and three years of upper secondary. Grades one through six are known as Prathom 1 – 6, while grades 7 -12 are known as Matthayom 1 – 6. Prior to 1977, the structure of school education was 4-3-3-2.
Students take national examinations at the end of years 3, 6 and 9. Prathom III students are tested in mathematics and Thai, while at the end of the primary cycle they are tested in mathematics, Thai, science and English. Secondary Grade 3 students are tested in mathematics, Thai, science, English and social sciences.
Schools attached to universities tend to be the most sought after, and students are required to sit for competitive entrance examinations, as is also the case with prestigious private schools. Admission to most public schools is open.