My grand son's class is studying the parable of the good Samaritan in school this week?

he is in catholic school, by the way, his teacher asked why the Samaritan was more moral than the other two people. he didn't understand the meaning of why he was moral. I told him its because a moral person will do what is right, even if it costs him and nobody watches or cares, a moral person does something just because he should. is this the answer I should have given him?