Chamber of Secrets is like just every other Harry Potter movie in that it ends with a happy scene filled with people celebrating a short-lived victory. Harry is probably thinking that next year will finally be a normal year at Hogwarts.
Think again, kid.
The students are gathered in the Great Hall. Dumbledore announces that everyone who's been petrified was successfully revived by the Mandrake harvest. Yay! Then he says that exams are cancelled. Double yay! Then in walks Hagrid. He's been freed from Azkaban and his name has been cleared.
The first thing he does is thank the three second-year students who cracked the case:
RUBEUS HAGRID: And I'd just like to say that if it hadn't been for you, Harry and Ron and Hermione, of course, I would still be you-know-where so I'd just like to say thanks.
HARRY POTTER: There's no Hogwarts without you, Hagrid.
Aww. That's sweet.
But, you've got to admit that it's a little sad that it took fifty years for someone to figure out that Hagrid didn't actually open the Chamber of Secrets. In all that time, Dumbledore couldn't have gotten Hagrid a pardon? Seems weird that a few twelve-year-olds were able to figure out that Hagrid was innocent, but no adults who actually lived in the castle bothered to investigate.
We're just saying.
In any case, justice was served, so hooray for Hagrid!