Responsibility for education oversight at primary and secondary level in Slovenia lies with the Ministry of Education and Sports. After non-compulsory pre-school education, children enter the nine-year primary school at the age of six. Primary school is divided into three periods, each of three years. In the academic year 2006–2007 there were 166,000 pupils enrolled in elementary education and more than 13,225 teachers, giving a ratio of one teacher per 12 pupils and 20 pupils per class.