Intended instruction time refers to the number of hours per year for which students receive instruction in both the compulsory and non-compulsory parts of the curriculum. For countries that have no formal policy on instruction time, the number of hours was estimated from survey data. Hours lost when schools are closed for festivities and celebrations, such as national holidays, are excluded. Intended instruction time does not include non-compulsory time outside the school day. It does not include homework, individual tutoring or private study taken before or after school.