Learn the difference between place as purpose (at school) and place as building (at the school).
at/in + place (purpose) | at/in + the + place (building)
Don’t automatically add 'the' before school/prison/hospital; check meaning.
Is the person using the institution for its purpose or just visiting the building?
💡 British vs US note: UK often says in hospital (as a patient), while US commonly says in the hospital. For school, both varieties commonly use at school for purpose.
✓The children are at school.
✗The children are at the school. (meaning: studying)
At school = they are there as students (purpose).
✓I’m at the school to meet the teacher.
✗I’m at school to meet the teacher. (if you are not a student)
At the school = the building/location (often as a visitor).
✓He’s in hospital. (UK) / He’s in the hospital. (US)
Variety differs; meaning is usually 'as a patient'.