From typicallyspanish.com

Basics
Education in Spain
By m.p.
May 23, 2007 - 5:30 PM

Education System

Education is compulsory in Spain between the ages of six and 16. The public sector is funded by the Spanish State and is free of charge, with the school year running from around mid-September until around the end of June. Specific dates depend on the area.

Many state schools will also have a nursery school section, (educación infantil) which is non-compulsory. It is split into two phases: up until three years old, and from then until the age of six. The second stage is free of charge, with teaching focused on developing physical and mental skills.

Primary education runs from six to 12 years of age and is organised in three cycles of two years each. Classes are all mixed ability, with subjects taught being Spanish language, a second language – usually English - maths, physical education, art, and ‘conocimiento del medio,’ which includes geography, biology and history.

Compulsory Secondary Education (Educación Secundaria Obligatoria – ESO), takes place in secondary schools (instituto) between the ages of 12 and 16, and aims to prepare the pupil for the legal minimum working age of 16, and provide the education necessary to continue with further studies.
Exams for the Certificate of Secondary Education, or school-leaving certificate – graduado escolar – are taken at the end of the four years. The pupil then has three options: to leave education, to remain on for further studies for the Bachillerato, or to study vocational training – formación profesional - in a vocational training school.

The Bachillerato from 16-18, is the last stage of secondary education in Spain and is voluntary. It is split into two courses with four separate modules on offer: arts, natural and health sciences, humanities and social science, and technology, and prepares pupils for the university entrance exam.