Well Alice, I think Christy the wordsmith ought to do better research. Like many words on English, "school" is an example of a word which has more than one meaning and origin.

The OED gives the following derivations

School as in learning and pupils derives from the Greek skhole meaning philosophy etc, via the latin schola meaning school, and the Old English scol

School as in shoal of fish is a Middle English collective noun for fish deriving from Middle Dutch schole

I think is clear that the prununciation of "Schole" has given rise to Shoal, whilst its spelling led to school.

Shoal it self is of course another example, Shoal ground is a quite different meaning from a shoal of herring!

Ah the joys of English!

Pete M