Prefect

A prefect at Hogwarts School of Witchcraft and Wizardry is a student that has been given some extra authority and responsibilities.

Prefects are allowed to take House points away from other students, but are not allowed to take points from other prefects. There was some confusion about this after the original release of Harry Potter and the Order of the Phoenix. It had previously been stated that prefects could dock points, but in a scene in the first printing of Order of the Phoenix Ron Weasley, Ernie Macmillan, and Draco Malfoy all either state outright or imply that prefects are not allowed to take points. This was pointed out as a mistake, and subsequent printings had a slightly different version of the dialogue, making it clear that prefects can take points, just not from other prefects.

Once a student becomes a prefect, they have a better chance of becoming Head Boy or Head Girl. Though it is not required to have had been a prefect to become Head Boy or Head Girl.

Hufflepuff

 * Hannah Abbott
 * Ernie Macmillan

Gryffindor

 * Hermione Granger
 * Ron Weasley

Ravenclaw

 * Anthony Goldstein
 * Padma Patil

Slytherin

 * Draco Malfoy
 * Pansy Parkinson

The above are almost certainly not the complete roster,as it appears one boy and one girl are chosen for each House as they enter fifth year,thus the fifth,sixth,and seventh year classes would each have a pair except the Head Boy and Girl may be chosen from among this number and may not be replaced.We are generally only informed about students in Harry Potter's year.

Gryffindor
Lily Evans Potter
 * Albus Dumbledore
 * Remus Lupin
 * Bill Weasley
 * Charlie Weasley
 * Percy Weasley

Hufflepuff

 * Cedric Diggory

Ravenclaw

 * Penelope Clearwater

Slytherin

 * Tom Riddle
 * Lucius Malfoy