Alright - I think there's potential for all four of my students, so let's just give ya the rundown, yeah?
The first one I think that has potential is Darcy. She's a sixth year Hufflepuff, but she's only spent about a year in Hogwarts total. She spends most of her time on a ship with her father, who is a magical treasure hunter. She is known well by her peers, though she doesn't have many personal relationships with them. She's known as the Pirate or the Sailor. Darcy is a good person - her manners have never been cultivated, so she drinks, swears, and spits out of ignorance. She enjoys meeting new people and HATES school.
Now for her polar opposite, Penny Macnair, who hates meeting new people and LOVES school. Penny is quiet, studious, and incredibly insecure. Her parents are blood purists and she is not, though she is the only one to know of her own doubts. She continues to parade as a quiet purist, though she hates the beliefs. Most people find a study buddy in her.
Now, Wally Abercrombie is a fourth year Ravenclaw. She is known around the school as the Australian transfer who transferred back to Australia, and then transferred back, suddenly looking like a babe. She's also known as a partial creator and distributor of drugs called Sugar and Spice. Wally is very withdrawn and does not often talk to people.
Then, Henri Finch. The American transfer fourth year. She's a sociopath, really. She subtly destroys the peace around her. She's currently in a very public flame war with Erika Dixon, making it seem as though Erika is the bully and she is the victim. She's very unstable right now.