Crossword Genius

That moralising upset numbers in old-fashioned school lessons (14)

Ross

I believe the answer is:

antilogarithms

'numbers in old-fashioned school lessons' is the definition.
(historical mathematical term)

'that moralising upset' is the wordplay.
'upset' indicates an anagram.
'that'+'moralising'='thatmoralising'
'thatmoralising' with letters rearranged gives 'ANTILOGARITHMS'.

(Another definition for antilogarithms that I've seen is " numbers of mathematicians".)

I've seen this clue in The Guardian.
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