The crowd surrounding the bulletin-board, the presence of the villagers in the class, the silence in place of the routine hustle and bustle of the school, the emotions that gripped M. Hamel and Franz, representing that of the teacher and the student community respectively, were all indicators of the realisation of the importance of their language to them.
In the story, M. Hamel says that people realise the importance of somebody or something in their lives very often when it is lost to them. Similarly, it was the order from Berlin that made people realise the importance of their language for them.