In vs At (In the school vs at the school.)

[Nola]

Could anybody tell me the essential difference between the usage of In & At with the places?
e.g In the farm vs at the farm.
In the school vs at the school.

[Yankee]

Hi Nola

Very generally speaking, 'at' refers to general vicinity, and 'in' has a more specific sense of containment (inside).

Without any further context, "in the school" suggests "inside the school building".
On the other hand, "at the school" is less specific -- it might mean 'in front of or near the building' OR 'inside the building'.
.

[Nola]

Hi Amy,
Many great thanks for your good explanation.