Assortative mating for things like IQ is known to increase genetic variance in subsequent generations, and hence increase heritability estimates. Given an initial starting point of low or modest heritability, assortment of this magnitude will increase heritability estimates over 4 - 5 generations.
Increases are cumulative.
Since it is known that institutions of higher education place people of similar IQ into proximity, and proximity is a major determinant of mating, it is not implausible that heritability estimates for IQ are higher now than they were 200 years ago. But this would not be due to directional selection, but rather to an incidental byproduct of assortative mating.