I don’t think grade 2 or 3 grades will paint the picture for them. Elementary school grades saturate quickly, there isn’t enough dynamic range. What IQ do you need to get perfect marks in elementary school? Sure, you’ll know you are above average, but the social experience for someone with a very high IQ is extremely different from someone with a slightly above average IQ.

I think the real problem is not providing enough challenge, so they get used to succeeding without trying and never learn the emotional side of trying and failing, until they can’t keep up anymore, which for really bright kids may not happen until they are basically adults.

If you praise for doing what they can do without trying, you get this problem. If you meet them at their level and actually challenge them from a young age, while also praising them for being clever, I suspect you won’t see this problem.

By analogy, is it harmful to tell a kid he’s naturally good at soccer, while providing the resources and coaching necessary to take advantage of the potential? I imagine the dynamics should be similar from the skill acquisition angle, the difference is just how the activity to perform is generated.

Totally agree. This is now the approach I’m taking with my 4 year old who is clearly quite bright.