Have a similar concept, about a male protagonist that goes to school to become a teacher, though the teacher in GTO is originally a yankee..
This drama is very similar to HAMMER SESSION since they both involve teachers, who solve the students' problems in unconventional ways.
Both these shows are about an unlikely teacher leading a group of unruly delinquent students to academic success(a High School Diploma)
Both are about teachers who really care about their students and teaches them life lessons. SCHOOL!! is like GTO only with elementary school kids.
The leads both possess a hidden personality, covering a goofy front with a passion for education. Both dramas deal with the school setting, bad teachers, bullying, and family drama. Both leads are eccentric, charismatic men with a penchant for taking unpredictable actions. If you liked GTO, I highly recommend Kazoku Game.
Both are about dedicated teachers with a unique personality. They care deeply about their students and try to help them in various ways. The episodes follow individual backgrounds of the students in his class, and deal with subjects like bullying, false accusations of sexual harrassment by a student, and family issues, etc.