This probably isn’t so new*, but it seems to be fairly pervasive just now. This being the aging-up of characters in movie adaptions of kids’ books presumably to snag a bigger audience. The book Percy Jackson is in middle school whereas the movie Percy is in high school. Same thing with Harriet Welch. And now it looks that way with Beezus as she too has been bumped up to teen status in the forthcoming Beezus and Ramona. Are there others you can think of?
* Just remembered teen Judy Garland as Dorothy Gale in the 1939 Wizard of Oz movie. (Dorothy is eight in the book.)