Could you please tell me the meaning of these lines?
a) "who worked right on tracing theirfish-hooks, as if that was French, too."
b) "they looked like little flags floating around in the room"
Thanks.

a) 'Fish hook' is the informal name given to the symbol used for a particular unuttered alphabet used in the French language - owing to its shape. In the story: the otherwise unmindful students were writing even that little symbol with fierce concentration, because even that represented to them their beloved language which the German government was taking away from them. 

b) On the day of the last lesson, M. Hamel, the teacher had new copies for his students - for their routine writing exercise, He made them write the words 'France' and 'Alsace' on these, an instruction the students followed only with enthusiasm. When the exercise was at an end, these papers with the names of their country and their home written in beautiful large letters, looked no less significant like national flags.