If you tell kids that they have intellectual ability, it makes them insecure and unwilling to try things they might fail at, so you should tell them that effort is what matters. If you say that certain fields of endeavor require innate ability, people who don't know that women and POC are liable to have innate ability will not hire them, and even worse, the women and POC themselves may believe it and not try, so you should tell them that effort is what matters.
Scott Alexander looks at the other side:
The obvious pattern is that attributing outcomes [fatness, sexual orientation] to things like genes, biology, and accidents of birth is kind and sympathetic. Attributing them to who works harder and who’s “really trying” can stigmatize people who end up with bad outcomes and is generally viewed as Not A Nice Thing To Do.
And the weird thing, the thing I’ve never understood, is that intellectual achievement is the one domain that breaks this pattern.