Intelligence has a number of different aspects. Most IQ tests do not actually provide an accurate intelligence quotient. As posted, you can do better on those tests with practise. I've known people with 140+ IQs who can't seem to grasp basic, obvious life lessons and live on benefits.
Most people can learn a subject matter if they are interested and the teacher is good. Some people obviously learn some things easier than others but trying to quantify that is only going to be crude at best.
I think they are culturally biased too, WTF does some kid in the amazon have to gain from knowing what shape a hexagon folds into?
Whats a British kid going to learn from attaining an outback Australian Aboriginal kids ability to memorize the positioning of nearly each little stone he walks past to work out what animals are about? memory is a massive component of intelligence but the Aboriginal kid is going to score low on the memory component of the IQ test because it is more concerned about memorizing lists in a certain order.
Singapore and South Korea score the highest on the global IQ rankings but travel to either country and youll see how fucking dumb the average person is. I was eating in a cafe in Singers years ago and kept having to ask the waiter for another glass of h20 (which came in tiny glasses), finally I felt bad so I said "Brother can you bring me a tall glass and save us both some trouble?" he couldnt he said water comes in short glasses, I pointed to my friends tall glass of coke and he still looked at me confused. I said fine then muttered "fucking retard" under my breath and dude heard and pointed out he wasnt retarded he was in fact a dentistry student..... there you go
South Korea, dont get me started on how dumb (some) people can be, on average they have much less common sense than in the west, shit my wife's small country town (< a couple hundred thousand people) has 15 vehicular deaths per day and there is hardly any traffic because they simply cant follow any direction. They actually also believe that korea is the only country that eats chilies/peppers