So, to answer your burning question: Emma Watson was 15 years old when she started playing Hermione in Order of the Phoenix. She turned 16 before the cameras stopped rolling. In your head, just say “She was sweet sixteen.”
Next time you watch the film, picture her backstage doing homework between takes. She was juggling potions (chemistry) and potions (magic). Actually, she did have a tutor on set. Real life doesn’t stop for magic.
And now you can casually drop this fact at your next trivia night. “Oh, Emma Watson? She was 15 going on 16 during the U.A. (Umbridge Administration).” Then sip your coffee like a boss.
That’s it. No more mystery. She was a young Hermione in the books, and a young Emma in real life. And they both survived the fifth year. Cheers to that.