1, in school means studying at school, emphasizing that the subject is the identity of the student, for example, we study English at school.
At school means at school, for example, my son was at school yesterday. My son was at school yesterday.
Extended data:
Comparison between in and at:
When used locally, at refers to a smaller place, such as a town, and in refers to a larger place, which is used in front of provinces, countries and the mainland. Before it was used in an international metropolis? And in, but in is usually used before London.
In should be used when referring to the speaker's residence, generally in means real existence, but at is not. When it comes to big buildings in big cities, at is often used before the names of big cities, such as the Pantheon? Where is it? Rome. Speaking of shops, institutions, schools, etc. If you think of it as a point, use at.
If you think a place is in barber's, Green's shop and so on, use at instead of in. Speaking of house numbers, use at, such as live? Where is it? Zhongshan Road 1 184, in should be used before the road name, and at should be used when saying "at the crossroads of ...".