I don't think the issue is intelligence but how were you raised and what values were emphasized by your parents.

'You are smart!' is one of the worst things you can say to your children. It places their own self image on a dependency of results in an ever increasing difficulty of tests.

'You did a great job this time! I hope you enjoyed the challenge!' places their own self image on their effort, not on the results.

It seems a small change, but the resulting mindset could not be more different.