Reasoning scores and academic results
The relationship is real and consistently found, and it is far weaker than popular accounts suggest.
The size of the effect
Reasoning scores typically explain a modest share of variation in school results. The large majority is explained by other things.
What explains more
Attendance, teaching quality, prior knowledge, home study conditions and conscientiousness. All are more open to change than reasoning scores.
The selection effect
The link weakens at higher levels of education, because the range of reasoning ability narrows once people have already been selected on it.
Scored against age, education and area norms. Free certificate with a QR code anyone can verify.
Questions people ask
Can a student with an average score do well?
Routinely. Average reasoning with strong habits beats high reasoning with poor ones.
Should schools test for it?
Only with a clear purpose and trained interpretation; a bare number does more harm than good.