Gokusen (2004) IMDb
A yakuza girl becomes a high school teacher, and is assigned to a class full of violent delinquents. She has to try to get some sense and hope into them without revealing her background.
School drama. Too stylized and childish a lot of the time, and some episodes are filler. Bad character design. The mobsters are amusingly portrayed as a bunch of outstanding citizens, never seeming to do anything “bad”. Real yakuza have extremely unpleasant methods, and I imagine a high school teacher would be background-checked.