Ok, I'm in the middle of Gokusen. Totally different My bad. The whole Yakuza clan, delinquent characters and principal who likes gardening background gave a reminiscent of My Boss My Hero. Both are fantastic anyway! Highly recommend it!
there is also a follow-up movie titled "My Boss, My Teacher" and is also very funny and lots of moral value on it! if there is a season 2 for this, the title would be the same above.. If you want a sequel though XD ho ho