One school: Hogwarts School of Witchcraft and Wizardry
Two Girls: A freak and a chatterbox
Three blood groups: Pure bloods, Half Bloods and Mudbloods
Four Houses: Gryffindor, Hufflepuff, Ravenclaw and Slytherin
Five boys: A rebel, a pandered child, a traitor, a werewolf, and a distressed boy.
The story starts with them...
Five, four, three, two, one- Avada Kedavra!
... and ends with them.