Here is the basic character skeleton, but there's no reason to restrain yourself to it. Add anything else that you feel is important. 

Name:
Gender:
Age:
Grade (9-12): 
Academic Status (AP, Honors, Regular, Special, Remedial):
Race/Ethnicity:
Hair Color:
Eye Color:
Height:
Build/Weight:
Background:

Students aren't the sole people involved in this RP; the teachers are victims just as much as their students. However, there are far fewer teachers than students, of course. Here is the basic character skeleton for a teacher.

Name:
Gender:
Age:
Grade (as in, which grade the teacher oversees; 9-12; also mention which level that their particular class is at, which can be AP, Honors, Regular, Special, or Remedial):
Subject (can be either an academic or elective course):
Race/Ethnicity:
Hair Color:
Eye Color:
Height:
Build/Weight:
Background: