The Ministry of National Education is responsible for pre-tertiary education. This is compulsory and lasts twelve years: four years each of primary school, middle school and high school. Basic education in Turkey is said to lag behind other OECD countries, with significant differences between high and low performers. Access to high-quality school heavily depends on the performance in the secondary school entrance exams, to the point that some students begin taking private tutoring classes when they are ten years old.