Is there any advantage to prepping a child for cognitive ability tests?

[Olivo]

Aren't they designed to assess 'natural ability/potential'? So wouldn't doing practice papers for weeks beforehand mean an inaccurate picture was painted of that child's ability?

No point at all IMO. The whole point about that sort of test is that it is random and whilst you can revise the same type of question, you cannot predict what kind of tasks will arise. It's not an exam with a syllabus you can revise.

What would be the value anyway, because if you could revise and predict what would be in the test, you would not have a real view of the ability of the child. How would that be of benefit in the classroom.

I agree with you foxy. I'm just not sure why the parent did it, or why the teacher suggested it when others were told there is nothing you can do before it.