I think I get it

Our son (11) brings home his school report.
He: ‘To sum it up, I have received top scores from basically all subjects, except for free discussion,from which I got a 3 on a scale of 5.’
Me: ‘How come?’
He: ‘Some of my classmates receive better scores, but they talk about all kinds of pointless blabla, while I only speak when I have something to say.’
Me: ‘But when is this class? Morning or during the day? And what are the topics? And you have to prepare? And..’
He: ‘I have said everything about this subject.’
Me: ‘Ok, I think I get it.’