A tactic my parents used on me in the 8th grade......embarrass me in front of my class.
I was a class clown/instigator early on and was always standing in the corner or the teachers moved my desk into the hallway so I would not disrupt class. Nothing seemed to work, I just couldn't sit there and listen.
So, after a parent-teacher conference, they decided my parents would sit with me in the classroom and that is the last thing I wanted. I would have been a laughing stock if they actually went through with it, but the threat was all that was needed.
Needless to say, I turned into a pretty good student from that day forward
This mom should have maybe tried something like this IMO, put on the proper attire and escort her through school
I realize it is different these days but it sure was effective.