Portrayed by Linda Emond in season one and the beginning of season two and by Jan Maxwell at the end of season two and for one episode in season four, Headmistress Queller is Constance Billiard School for Girls' and St. Jude's School for Boys' headmistress.
Portrayed by Amanda Setton in seasons one, two, four and five, Penelope Shafai is a member of Blair's clique until she was dethroned as queen bee; and constantly shifts her allegiance between Blair and Jenny.