Why does Franz feel ashamed after learning that this is his last lesson?

Franz feels ashamed after learning that this is his last lesson because he realizes how little effort he has put into his education. In that moment of clarity, he recognizes that he has taken his language and lessons for granted, neglecting his studies while enjoying the carefree aspects of childhood. This sudden awareness of missed opportunities fills him with regret, as he understands the importance of the knowledge he now longs to grasp fully. His shame is compounded by the realization that he will never have the chance to learn from M. Hamel again, making his lack of appreciation all the more poignant.