Faulty contribution to maths instruction (4)

I believe the answer is:

sins

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'faulty contribution to maths instruction' is the definition.
I can't judge whether this definition defines the answer.

'contribution to maths instruction' is the wordplay.
'contribution to' says the answer is hidden in the clue.
'SINS' is hidden within 'maths instruction'.

Can you help me to learn more?

(Other definitions for sins that I've seen before include "Breaches of moral law" , "Transgresses" , "Serious offences" , "Evils" , "Wrongdoings" .)

I've seen this clue in the Evening Standard.

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