The setting might change from high school to college.
He's older than I would have expected based on the casting speculation surrounding this film. Most of the final candidates are genuine teenagers, while Garfield is 27 right now. Originally, the Jamie Vanderbilt script for this film had Peter Parker as a high school student, and the assumption was that Sony would cast young so that they could do several films over the course of high school and college, a la the Brian Bendis take in "Ultimate Spider-Man." What we're hearing now though is that Parker starts the series as a college student, and that makes more sense with this casting
That's probably why they went with an older actor.