In the anime the story is somewhat cliche: troublesome high school students with peculiar skills or traits trying to rid a teacher who's trying hard to to teach them a lesson in life. However, there are some very clever surprises and plot devices to keep the viewer poised for more. My only complaint is the rather hashed season finale (Ep. 42 and 43), but that was to be expected since those are the only two episodes that didn't diligently follow the manga.
The reason why you should watch or read this manga is simple: Onizuka Ekikichi, 22 years, virgin. This series is all about character, rather a character. Truly GTO is ineffable in that sense. While there is a certain moral message in this series, watch it for the sheer fun value. It will make you laugh, that's for certain, perhaps it might even make you cry. The live action series, is quite impressive and worth to watch too.
Eikichi Onizuka is a 22-year-old ex-gang member and a virgin. While peeping up girls' skirts at a local shopping mall, Onizuka meets a girl who agrees to go out on a date with him. Onizuka's attempt to sleep with her fails when her current "boyfriend", her teacher, shows up at the love hotel they are in and asks her to return to him. The teacher is old and unattractive, but has sufficient influence over her that she leaps from a second story window and lands in his arms.
With these realizations, he sets out to become the greatest teacher ever, using his own brand of philosophy and the ability to do nearly anything even when under enough pressure. He is hired as a long-shot teacher by a privately operated school to tame a class that has driven one teacher to a mysterious death, another to nervous breakdown, and one other to joining a cult. He embarks on a mission of self-discovery by breaking through to each student one-by-one, and helping each student to overcome their problems and learn to genuinely enjoy life.Here is the link for the manga, anime, and drama of GTO. Even it's a old series but it's good to watch the drama and movie cause the other it's a really good actor.
GTO - Drama
GTO - Anime
GTO - Manga