The intercultural calendar of the Federal Office for Migration and Refugees shows the variety of holidays and memorial days of different religions and cultures that live together in Germany. Therefore, in addition to the most important holidays from Christianity, Judaism, Islam, Hinduism, the Sikhs and Yazidis, the Intercultural Calendar also includes legal and other observances of various cultural traditions www.bamf.de/SharedDocs/Anlagen/DE/Downloads/Infothek/Sonstige/interkultureller-kalender-2018. For high holidays of other religions there are in some states the possibility to let children from the school lesson.
In Hamburg, pupils get school-free for special religious holidays listed in the overview: http://www.hamburg.de/contentblob/3031278/4a838a9dd081b18a51b853d5cf678cab/data/feiertage.pdf