It's not all the Juniors. Some of them, though.

There was a YPL game today and it was meant to be every student for him or herself. But they all worked together. And they chose the winner beforehand and everyone made sure that she won. That was Luna.

So I don't think they're in terrible trouble but Madam Umbridge obviously didn't like that they didn't play by her rules.

Actually, Harry did really well at keeping everyone organised and focused.