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IQ tests are perfectly reliable for predicting learning disabilities. If someone scores very low on an IQ test, they will not function well in a normal school. Neither will the function well if they score very high. They’d be bored out of their minds.

I’m struggling to understand your problem with IQ tests. If you have an IQ of between 90 and 110 as per a standard test no one really cares. You’re “normal”. Score higher maybe a bit more intelligent at spacio-temporal problems and it’s probably a good predicator that you’ll do well at mathematics.

If you score below 75 you almost certainly have an intellectual disability and need help. You can give these people any other test you like, it will make no difference. They won’t “function” in a society where the mean IQ is 100 (which it is).