The question is notwithstanding how IQ seems relatively fixed through the lifespan
I think that's the same thing as asking the question independent of whether IQ has enough validity to scientifically explain rather than just measure intelligence.
I am also assuming that "intelligence" - as it is measured by IQ tests - is learned.
If each year a child is just 3% disadvantaged at obtaining the skills necessary to do well at intelligence tests, across the 11 years of school this works out at roughly 70%: the mental age of someone with a learning disability, right?
Let's suppose that 50% of variance in learning is explained by environment and teaching etc., roughly the same as IQ scores in adulthood.
Does that mean that - on average - an adult with a learning disability but no genetic differences to the population mean, will have been 6% worse at learning what is necessary to pass IQ tests each year they were at school?
Is disadvantage cumulative across childhood development?
By 3% or 6% disadvantaged I just mean learning - the skills that IQ tests measure - at 97% or 94% capacity: due to environmental differences.
What meta or theoretical mistakes or false assumptions have I made?