Up until the 1970s, compulsory education was provided in the six-year folk school. After four years of folk school, a part of each age group moved up to the secondary school, which was divided into the five-year lower secondary school and the three-year upper secondary school. In the 1970s, a nine-year compulsory school common to the entire age group, i.e. the comprehensive school, was created on the basis of the folk school and lower secondary school.