Pass, even in school (3)

I believe the answer is:

col

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'pass' is the definition.
(col is a term for a mountain pass)

I don't understand how the rest of the clue works.

(Other definitions for col that I've seen before include "Low point of saddle between two peaks" , "Mountain saddle" , "Low point of a ridge" , "Mountain defile" , "A depression in mountain range" .)

I've seen this clue in the Sydney Morning Herald.

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