Harry Potter The order of the pheonix PS2 trouble?

I finished battling voldemort in my Harry Potter The order of the pheonix for the PS2. For some wierd reason umbridge is still in office as the headmaster, when in the story Dumbledore takes over at the end. It also keeps on saying that I only completed 59% of the game. I don't understand! How do finish ur O.W.L.S Please be descriptive. Thanks!