Was the age of the students a factor in the filming of the Harry Potter films?
Watching the Harry Potter films you gradually see Daniel Radcliffe, Emma Watson and Rupert Grint get older as if matching to the year they are in Hogwarts.
For filming, were the ages of the students a factor? I.e. filming of at least the first 4 films each had to be done within a year so that with the next film, at the very least Daniel, Emma and Rupert didn't look too much older for the next film and if done early they had to wait a little bit.
The actors were (+-a year) the same age as the characters. They filmed roughly one film a year so this remained true throughout.
The age of the students was massive factor in casting. Quotes from the casting director, Janet Hirshenson (source):
It was really specific on ages because there were several movies hopefully, so we could not go for a small 13-year-old to play anybody. They had to be at least the proper age of the character.
I know at one point there was a push for the actor who did ‘Billy Elliot.’ He was a really good actor, but he was 14 years old. It’s like, ‘No, he was 14 years old. It just can’t be.’
Note she says "hopefully", so they couldn't have been planning to film all four then-released books in one go. Also, they clearly age appropriately between each film: