James started going to school at the age of six. So now he's been at school for ten years.
James started going to school at the age of six. So now he's been in school for ten years.
which is correct?in school or at school?
Both make perfect sense. "At" is used to describe general location. When you say he has been "at school", it means he has been going there. "In" describes containment (in a general sense), not just in the building itself but also in the sense of participating there.