Barbara wasn't loathed at school...
Descriptions (and Sheba) state that students and staff at the school loathed Barbara. I think they found her a bit disagreeable, but still respected her. The exception would be the headmaster/principal who did not like Barbara challenging his authority.
High school students generally do not behave for a teacher they loathe. They may not like the teacher as a friend, but at that age, they must respect the teacher to comply with him/her.
Also, I don't think Brian and other teachers would confide their personal secrets and thoughts in Barbara if they truly loathed her. I think they were somewhat intimidated by her, but again, respected her.
We came to wreck everything and ruin your life. God sent us.