You don't tell them they are dumb or anything. You just let them exist as long as possible without labeling or self-labeling. I know it is just a saying, but I think the research backs it up: Hard work beats talent when talent doesn't work hard. Effort and discipline must come before "smart". It's okay to smart, it isn't like we shame it or anything, we just don't focus on it. We read advanced books and do all sorts of "smart" things in the house, but we don't label it or compare it. Smart is a thing that really breaks out your "comparing mind" as they call it in buddhism. The author had the same issues, feeling a bit smug compared to all of the average kids. That is the comparing mind in action and it all sets you up for potential failure.