Actually, he started the group in secret without telling anyone outside the class. But the director begun suspecting things since the group became active outside the class as well, so the teacher has to tell him everything. IIRC the director didn't liked the idea, but said that the experiment have to stay within the class itself, and if it goes out of hand, he has to stop the experiment immediately. But it was actually already too late at that moment, since the group already started with making the school one big group at that moment....