With a history of leading a motorcycle gang and getting bad grades in school, why would 22 year old Onizuka ever want to become a teacher? Is it to educate young minds or spread the joy of education? Sure, if it involves being able to look up high school girls' skirts! Watch as this would-be educator uses his own life lessons and unconstituted methods as a means to control a delinquent class of students -- students who certainly aren't as happy to have him as a teacher as he is happy to be teaching...
Denpa Kyoushi takes a lot of elements from GTO, but replaces the ex-biker teacher with an otaku one. If you like otaku main characters and you liked GTO, you probably should give Denpa Kyoushi a try.
Both of the teachers in GTO and Denpa Kyoushi resort to... creative teaching methods and do their best to help their students out in ways that defy normality. It's all in good, comedic fun and the teachers have good hearts and the best of intentions for their pupils.
Yamaguchi Kumiko is next in line to be the boss of the Kuroda Ikka yakuza clan due to her parents' death. However, fresh out of college, Kumiko decides to pursue her lifelong dream of being a teacher. Now hired as a mathematics teacher at an all-boys school, Kumiko must hide her true identity. She's assigned to class 3D, inhabited by the worst of the worst delinquents. Popularly called "Yankumi" by her students, she tries her best to gain the respect of and offer help to these students who'd like nothing more to make her life a living hell.
Both titles are telling a story about a very unusual teacher, having been assigned to class full of problematic kids. The teacher have to gain his/her students trust, by helping them get through the problem they face and/or the troubles they cause. Both mangas go for "school should teach a way to live" theme.
Both main characters are good at fighting and have some sort of violent past ( bikers gang in case of Onizuka and yakuza family in case of Kumiko). The main difference is their gender, and the gender of potential readers (GTO is shounen while Gokusen is Josei)
Both GTO and Gokusen are based on similar idea. Both revolve around a high-school teacher coming from not so normal environment. In case of GTO it is a motorcycle gang and in case of Gokusen it is yakuza. Similar situations appear in both of those manga, however they are usually resolved differently. That is mainly beacuse Onizuka and Yonkumi have different personalities and lets not forget opposite sex. You will probably like one of those if you liked the other, but odds are you might even like one of those if you didn't like the other.
P.S. Gokusen has more conclusive ending and even some extra chapters taking place after the main manga.
While Rookies is a sports manga, and GTO is simply school life comedy both have very similar setting.
In both cases a new, unusual teacher comes to a school, and starts changing it by gaining student trust. There are some problematic students he have deal with - In GTO case it's whole class, that wages a wart agains teachers. In Rookies case it's a Baseball club that have a lots of deliquents.
A teacher enters a school and changes things for the better, influencing the students in school one at a time and for some, giving them a purpose in life. That is both of these in a nutshell. Going more into it, Rookies takes the form of baseball and the ones more directly influenced by the teacher are those in the baseball club as opposed to GTO's class of students.
Both are comedy driven with some bits of drama between the students and with their backstories but the vibes are the same and if you don't mind baseball being a large component of your manga then they are a great pair of uplifting, entertaining comedies that nicely compliment each other.
Because of similar main characters both series reminded me of each other. Both are delinquents, both are incredibly strong and incredibly dumb, yet both have something in them that can influence others. So, if you liked the male lead in one series, you might want to give the other series a go.