This, I should think, is a hint as to why he gets frustrated sometimes when he teaches his music class. Since he doesn't really have much of a clue as to what the home lives of his students are like, he can't quite figure out that what looks like a child who just doesn't bother trying is a child with unsupportive parents like Elly and John. Since he doesn't understand parent-speak any more than he understands children, he can't spot wretched parenting when he sees it like most of us can.
He also seems to not understand something else about children in that it never actually occurred to him to ask Michael what instrument he's actually interested in. A goofy confirmed bachelor who only deals with children in a classroom setting if at all might be excused for not getting that it wouldn't be the end of the world if he asked the child what he wanted. Not so much the boy's father, as I will explain tomorrow.