Compulsory education, or ''grunnskóli'', comprises primary and lower secondary education, which often is conducted at the same institution. Education is mandatory by law for children aged from 6 to 16 years. The school year lasts nine months, beginning between 21 August and 1 September, ending between 31 May and 10 June. The minimum number of school days was once 170, but after a new teachers' wage contract, it increased to 180. Lessons take place five days a week. All public schools have mandatory education in Christianity, although an exemption may be considered by the Minister of Education.