Great Teacher Onizuka

Great Teacher Onizuka (aka GTO) is a manga and anime series created by Tohru Fujisawa.  The main character is a former gang member who decides that he wants to become the best teacher in Japan.  He uses unorthodox methods to get his notoriously rowdy and undisciplined students in line. 

Both the anime and manga versions of GTO were released initially by TOKYOPOP in the U.S.  Funimation reissued the anime series in two box sets a while ago, so you should be able to find the anime pretty easily.

Below, you'll find some art from the anime.