“School as counter-public” is the hermeneutic key with which Ralf Koerrenz interprets the school model of the Jena Plan. Similar to the Dalton-Plan or the Winnetka-Plan, the Jena Plan is one of the most important concepts of alternative schools developed in the first half of the 20th century as part of the international movement for alternative education, the “World Education Fellowship”. Peter Petersen’s “Jena Plan” concept must be understood from his educational philosophical foundations. The didactic levels of action at school (teaching, learning) as well as the reflection of theory in pedagogical practice are made understandable by “school as a counter-public”. Not least with a view to the today’s Jena Plan schools, the question is asked for a context-independent core of what makes a school a Jena Plan school. The opportunities and ambivalences of the model thus become equally visible.