Unfortunately, it's also highly heritable, so environmental interventions have a fairly marginal effect on it.
(a) The Flynn Effect demonstrates that IQ is quite responsive to environment.
(b) The heritability of a trait is not a measure of the degree to which that trait is genetically determined: Highly heritable traits can be environmently malleable. (The heritability of height is 0.8, but nutrition, childhood sickness, etc. have a huge effect on height.) Conversely, traits with low heritability can be strongly determined, genetically. ("Number of eyes" is a trait with low heritability, for example.)
(c) The measured heritability of IQ isn't especially high. It's usually found to be in the vicinity of 0.3.
(a) The Flynn Effect demonstrates that IQ is quite responsive to environment.
(b) The heritability of a trait is not a measure of the degree to which that trait is genetically determined: Highly heritable traits can be environmently malleable. (The heritability of height is 0.8, but nutrition, childhood sickness, etc. have a huge effect on height.) Conversely, traits with low heritability can be strongly determined, genetically. ("Number of eyes" is a trait with low heritability, for example.)
(c) The measured heritability of IQ isn't especially high. It's usually found to be in the vicinity of 0.3.