My DS6 is a bit younger than Portia's son (and your DD), so I may not have as refined a view within this conversation that you both have.
Preamble aside, my view is that the core of addressing the idea of exceptionality is to:
1. Minimize the extent to which exceptionality is communicated as a valenced value judgment of the child and others, and
2. Normalize (meaningful, safe) failure and (healthy) striving in the zone of proximal development as a healthy part of life.
For the first item, each person is a constellation of skills, interests, temperament, and environmental influences. Similar to how Portia has framed the issue, I've told DS that there is value in people having with different strengths and weaknesses, and much of who we become is a product of how we see ourselves and choose to act.
Other significant adults and I provide honest feedback to him on his performance (absolute and relative, as appropriate), and he is encouraged to engage in honest self-reflection as he sets various goals for himself. In many areas, he performs several years ahead of age-peers, and he is aware of his relative placement in the group but, perhaps, not the absolute magnitude of the gap.
The discussion has been framed around needs to de-personalize the differences ("you need to do mixed fractions, your friend needs to work more on addition".) That way, when he encounters an area of weakness, he doesn't feel shame (or feels less) for lagging in skill; it's just another skill to work on at the appropriate level for him.
That point dovetails into item 2. I've made a concerted effort to keep DS engaged in his ZPD for the academic subjects he most enjoys, and it's paid dividends. He's learning to push through tough problems and be okay stepping back from a challenge to plan his approach. This has been helpful in minimizing the instinct we all have to seek instant gratification. But, I think more importantly, it's teaching him to rise to the occasion and see himself as a person who faces challenges head-on. Self-efficacy is a beautiful gift, at any point in the developmental spectrum.
Sometimes I remark on the level of what he has accomplished when he has persevered through a particularly difficult task, and I find this has fueled intrinsic motivation when he hits a lull. He likes being competitive and, while he seems naturally outwardly competitive, he's developing (what I think is) a balanced sense of competition with himself. As long as the attitude isn't cut-throat or supercilious, I see this as an affirmation of him as a person and an acknowledgement of the positive ways in which he uses his talents.
Another way I've approached this is to have him participate in activities particularly where he is not the best in the group. He needs to learn that he will fail or be out-classed at various points, and he needs to learn how to manage that behaviourally and emotionally.
The messaging I'm trying to give him is that it's okay to be beaten by someone who has genuinely out-performed you, and it's a cause for celebration when people use their talents to the best of their abilities. Everyone will win and lose, and we need to learn to do both graciously. When you're not top dog, you can either re-skill and re-evaluate your approach to perform better next time, or congratulate the winner and move on productively. But, a best effort is always meritorious.
I also regularly model failure and talk through my thought process, feelings, and decisions. I want to normalize healthy failure as a great step in learning and self-improvement. (It's also a great equalizer--children love to see their parents be honest about their own clay feet!)
Small brag: One of my favourite things I hear from DS is his out-loud self-talk when he does challenging math. Last week, I caught him muttering to himself under his breath as he worked, "Man, this is HARD. I've solved hard problems before, but this is really hard. Well, let's see if this works..."
I would LOVE to hear your thoughts on how you approach these topics with your DD and DS. As you can see from this novel I've written (and my signature!), self-efficacy is a personal favourite subject, and it fascinates me to learn how others are approaching this important subject with their children.
