I have just finished the Korean drama Hello My Teacher aka Biscuit Teacher & Star Candy.
Na Bo-ri (Gong Hyo Jin) is a 24 year old woman who has passed her teacher's certificate with the lowest grades and all she can become is homeroom teacher. She applies to several schools, but the one school she really wants to teach at is her old school from which she was expelled. Her art teacher Ji Hyun Woo (Kim Da Hyun) is still there and she still has a huge crush on him. But in order to teach at her old school the principal who incidentally is the older sister of said art teacher, makes her sign a contract to essentially babysit Park Tae-In (Gong Yoo) who is the step-son of the Principal. Tae-In is a troublemaker whose father (a famous medical doctor) thinks he needs to be locked away in a psychiatric ward. Na Bo-ri has to keep him in line as a last effort before the 19 year old will be locked away for good.
( read more - spoilers ahead )