here's a little more.

That afternoon Harry and Hermione sat very close together and planned their party.
They were going to hold it in the room of requirements (oh yeah, I forgot to mention- the plumbing in Hogwarts is not fine, and they returned back to their usual school, very grateful to the kind people of Poulard, but thinking it best to get as far away from John Howard as possible).
And this being the case, there wasn’t much planning to do, because they knew that the room would have everything they needed inside it when they arrived. All they had to do was invite all of the 5th and 6th years, but they were sitting together organizing it because as previously mentioned, they were very much in love by this point in time.
‘Oh, I have a great idea!’ Harry exclaimed. ‘Let’s invite the Elite Evil, too. They’re all great singers… but not as good as you, my love.’ He added, after seeing the look in Hermione’s face.
So it happened that the next night, all 5th and 6th years reached the room of requirements

thankyou very much Caity