In recent years, some school cases have become widely known. When mobile phones were brought in secretly, these cases all used mobile cell phone jammer to send out alarms. In 2013, the school supervision agency of the Schleswig-Holstein State Ministry of Education asked grammar schools to stop using such detectors because there was no legal basis. Whether such channels violate applicable laws depends on their technical design.
At least for jammers (also called "mobile phone jammers", which should actively prevent mobile phones from receiving signals), the requirements of the Telecommunications Law should be applied. Accordingly, the use of frequencies is only allowed if permitted by the Federal Network Administration or other regulations. If schools use such launchers, they will at least be threatened with fines. If devices allow locating or otherwise collect personal data, they will also be a problem in terms of data protection laws. Regardless of these issues and the technology used, it is doubtful whether the technical barriers are proportional to the detector, and whether it makes sense from an educational point of view.