The Wuppertal school sent a letter to staff in February saying Muslim students had been using prayer rugs and performing ritual washing in the restrooms and that they should get a "friendly reminder" it's not permitted and will be reported to the administration.
After criticism when the letter was posted on Facebook, municipal authorities said the wording was "unfortunate" and the school had only meant to bring affected students in to discuss a solution to allow their prayer, Bild newspaper reported on Thursday.
Authorities say the school was, however, legally allowed to stop people "praying in a provocative manner".