Gavroche is really fond of Sabriel! In all honesty, he's fully aware of how stubborn and eager to fly off the wind and do whatever he wants he is--and he realizes that the fact that Sabriel hasn't lost her temper yet is amazing. I think he also kind of gets why she's worried, but doesn't quite know how to vocalize 'I'm fine, I just want to push my limits' since he never really says what he's feeling OUT LOUD, y'know?

He has mucho, mucho respect for his teacher. You can tell because he'll actually shut up when she's talking.