There are state schools in the majority. Some schools are in ecclesiastical sponsorship, but awarded the state-recognized degrees. There are some private schools that charge different levels of school fees (https://mbjs.brandenburg.de/bildung/gute-schule/schulen-in-freier -traegerschaft.html and list https://www.berliner-privatschulen.de/brandenburg/liste).
After primary school there are three types of school in Brandenburg from year 7.
High school – Oberschule
The Oberschule covers grades 7 to 10. At Oberschule, the Advanced Vocational Graduation (Erweiterte Berufsbildungreife - EBR) and Middle Maturity (Fachoberschulreife - FOR) may be obtained. A special task of the Oberschule is to teach qualifications and competences for later professional development. There are Oberschulen where pupils are put together in classes according to the aspired school graduation (cooperative organized Oberschule) and there are Oberschulen, which use a course system with two levels (integrative organized Oberschule) in some subjects. https://mbjs.brandenburg.de/bildung/allgemeinbildende-schulen/oberschule.html
Comprehensive school with upper secondary level
The comprehensive school with upper secondary level includes the grades 7 to 13. The following qualifications can be obtained: Advanced Vocational Maturity (EBR) and Middle Maturity (Fachoberschulreife - FOR) after class 10 and Graduation from High School/ General University Entrance Qualification after class 13.
https://mbjs.brandenburg.de/bildung/allgemeinbildende-schulen/gesamtschule.html
High school - Gymnasium
The Gymnasium covers the grades 7 to 12. It provides a deepened general education and includes the education to acquire the General University Entrance Qualification after class 12.
https://mbjs.brandenburg.de/bildung/allgemeinbildende-schulen/gymnasium.html
Information about the vocational schools you will find in the age group 16-18.