I recently heard an actual example of the way that IQ scores, expressed as they currently are - in terms of percentiles, will confuse a stupid person.
The percentile expression is simply too complex, mathematical and abstract for general usage; and too incomprehensible to serve their proper function. Instead, intelligence (in children) should be expressed as IQ Age
In my real life example; a headmistress assumed that an eight year old child with an IQ of 120 should be moved up two classes to be taught with ten year olds; then the Head could not understand why the eight year old child was struggling to keep up in the new class.
Having previously been at the top of the class among 8 year olds, the moved-child was now scoring below average in class tests compared with ten year olds. Since the child's class position had plummeted, the Head thought that the fault must lie with the class teacher.
It emerged that the headmistress believed that children of all ages that had a measured IQ of 120 were of the same cognitive ability, and should be taught together.
When an attempt was made to explain the true meaning of IQ 120, the Head simply could not understand, and dismissed the objection.
Now, clearly this was an unintelligent head teacher, but the fact is that some head teachers are unintelligent - and they simply cannot understand the true explanation of how IQ scores are generated, and what they mean.
But, all is not lost, because even unintelligent head teachers can understand 'Reading Age' because it is much easier to understand. If the Reading Age of an 8 year old is 9, then it means that the 8 year old can read as well as the average 9 year old.
So, if such an 8 year old child was put up one class to be taught with 9 year olds, then their reading performance would be average for that class; but if the child was put up two classes to be taught among 10 year olds, their reading performance would be below average for that class.
So if an 8 year old with an IQ of about 120 instead had their intelligence expressed as IQ Age equivalent to the Reading Age; then the head teacher would have been told:
"This eight year old has an IQ Age of (about) nine-and-a-half."
The Head would then have understood that when the IQ 120 child was moved to a class of ten year olds, that child would be expected to perform at a lower than average level (because an IQ Age of about 9.5 is obviously less than the class age of 10).
Note: Of course this IQ Age method of expressing IQ is not possible among adults, or for older children substantially above average intelligence, because IQ scores level out at about age 16 for women and 18 for men.
This means that there is an age and intelligence ceiling on the IQ Age measure.
But the main and most important use of IQ testing is among younger children - so this would not be much of a problem in practice.
And, if necessary, a combination method could be used - so a 16 year old girl with an IQ of 125, could be said to have an IQ Age of 'Plus 25%' or something like that.
But among children up to about 13-14, and not of super-high intelligence, IQ Age would be a superior expression. The advantages of clarity and comprehensibility surely outweigh the limitations.