Harry decided to start with a basic test, asking all applicants for the team to divide into groups of ten and fly once around the pitch. This was a good decision: The first ten was made up of first years and it could not have been plainer that they had hardly ever flown before. Only one boy managed to remain airborne for more than a few seconds, and he was so surprised he promptly crashed into one of goal posts.
The second group was comprised of ten of the silliest girls Harry had ever encountered, who, when he blew the whistle, merely fell about giggling and clutching one another. Romilda Vane was amongst them. When he told then to leave the pitch, they did so quite cheerfully and went to sit in the stands to heckle everyone else.
The third group had a pileup halfway around the pitch. Most of the fourth group had come without broomsticks. The fifth group were Hufflepuffs.
“If there’s anyone else here who’s not from Gryffindor,” roared Harry, who was starting to get seriously annoyed, “leave now, please!”
There was a pause, then a couple of little Ravenclaws went sprinting off the pitch, snorting with laughter.
Harry Potter and the Half-Blood Prince – J.K. Rowling