Annual teaching or examination period during which students attend courses or take final examinations, not taking minor breaks into account. It may be shorter than 12 months, but would typically not be shorter than 9 months. It may vary for different levels of education or types of educational institutions within a country. This is also referred to as the school year, mainly for the pre-tertiary level.
ISCED 2011
http://uis.unesco.org/sites/default/files/documents/international-standa...