I will some recommendations on dramas with school setting, in particular high school setting. I wanted the focus to be on the interaction between teacher and students, something like Jdorama Gokusen and GTO. I had not watched much modern kdramas.
The only kdramas I watched are historical drama like Dong Yi and Jewel in the Palace. Besides these two historical dramas, the only modern dramas I watched is boys before flowers.  I enjoyed boys before flowers for its romance, but wanted to look for something more of interaction between teacher and students rather than romance. I had not watched such genre type in kdrama.
I will like the focus of the drama to be interactions between teacher and students, and preferred it to be in high school setting although I am fine with any school setting, whether it is preschool, junior school, college or university. Thanks for your recommendations.

Possibly The School Nurse Files (it's very odd and fantasy and FL is the school nurse instead of a teacher but she's also kind of a mentor to some of the students).