Admission to the Spanish university system is determined by the nota de corte (literally, "cutoff grade") that is achieved at the end of the two-year Bachillerato, an optional course that students can take from the age of 16 when the period of obligatory secondary education (Educación Secundaria Obligatoria, or ESO) comes to an end. A number between 1 and 10, the nota de corte is a combination of the grade achieved from the Bachillerato exams which the students take at school, and the average grade (nota de media) obtained from the university selection exam (commonly known as la Selectividad but officially named "Prueba de Acceso a la Universidad" or PAU) that the students will take at the local university.
The most popular courses at public universities demand the highest nota de corte, while for private universities cost is normally the factor that determines which course a student will follow (that is, the most popular courses are inevitably the most expensive).