School attendance in Austria is compulsory for all children permanently residing in Austria, irrespective of their nationality, and lasts for nine years. Enrolment can take place at a public (free of charge) or private (fee-paying) school.
Compulsory schooling begins at the age of six. Children can go directly into the first year of a primary school (Volkschule) where they will complete a four-year program or join a pre-school class (Vorschulstufe) if they are not yet ready for school.
School years 5-8 may be completed at middle school (Mittelschule) or at an academic secondary school (AHS). Schooling can be continued at the upper level of an academic secondary school (Years 9-12) or at a technical and vocational school or college (Years 9-10 up to Year 13). Since the introduction of the ‘Education until 18’ initiative in 2017, all young people are obliged to continue in some kind of education or training until they are 18 years of age.
You can find a complete overview of the system here.