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 are stories about passionate teacher, dealing with class full of deliquents. Students are always causing a lot of problems, yet they are slowly reformed by the unusal way of teaching, that new teacher employs.
Both main characters are good fighters.The main difference is their gender, and the gender of potential readers (Rookies is shounen while Gokusen is Josei)
Both series are mainly about a teacher and a group of delinquents, a group the school frowns upon and one such group that the teacher tries to help out and make them less delinquenty. Slap on some comedy, authentic delinquent attitudes and some rough charm and you got yourself some fine series that run for a nice chunk of volumes.
Also of note are the different art styles, which are as different as they come. Radically so. None the less, if you like anything dealing with delinquents and assorted school life antics, check 'em out.
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...
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.
When Koh was eleven years old, he lived a quiet and peaceful life, delivering sporting goods for his family's store and batting frequently at the Tsukishima Batting Center. Though Koh had no interest in baseball, he started the play the sport anyways after a series of events, much to the delight of his best friend, the beautiful Wakaba Tsukishima. However, soon life dealt Koh a tragic turn, changing him forever. Now, years later, Koh attends Seishuu Academy and is soon pulled back into the world of baseball. Alongside Wakaba's talented sister, Aoba; old friend and fighter Nakanishi; and plenty of new teammates and companions, Koh will once more pick up the pitcher's mitt and see if he has what it takes to be a champion.
Baseball. The name of the game and the primary focus on both series, with the rules given in depth and things are explained so you wouldn't get lost as easily. What really differs is the content outside of baseball. Cross Game, as opposed to Rookies has a greater hand in things unrelated to baseball, from developing relationships and having a greater emphasis on characters unrelated (Directly to baseball). More hints of romance, pretty much no swearing with little violence and little of anything to do with actual class stuff or teachers. But the passion of baseball is there and the dedication is within the pages. It's more laid back than Rookies and sometimes plays out like it's snapshots of a week in the lives of the youngsters but in the end, what brings everybody together in either series, is the love of the game; Baseball.