It's two years after the original events of GTO and this time Onizuka is teaching in a high school. Specifically, a class full of celebrities. But, like always, it's the problem class of the school. In true GTO fashion, Onizuka has to reform his delinquent students individually in unorthodox ways that can only be described as "LEGENDARY".
It's still GTO. Whether you dislike or like the original GTO is going to determine your enjoyment of this one, because the series didn't trip a beat in terms of really anything. I personally find it kinda disappointing that we don't have any of the Class 3-4 people returning (other than tomoko at some points), as there was a lot of character in Kanzaki, Yoshikawa, Uehara, etc. but the new characters introduced in the class serve pretty well, just don't be surprised if you don't find yourself as attached to Class G as much as Class 3-4 from the original.
Other than that, there's nothing I could say good about this series that couldn't also be said about the original. It's pretty great.