There are framework curricula in every federal state, where the aims are set. Every school is responsible to carry out the curricula and to establish its own concept to do so.
The curricula for general education schools and vocational schools in Niedersachsen can be found here: http://nline.nibis.de/cuvo/menue/nibis.phtml?menid=116&PHPSESSID=aecf535165df6efd75ff1984d3e02d08
The curricula of the vocational schools in Niedersachsen can be found on the website: http://www.nibis.de/nibis.php?menid=303