The reason for this has been discussed a lot, but the jist is that telling kids they are smart causes them to feel like there is something wrong with them when they try new things and fail ("I'm smart, why can't I solve this??!"). Praising hard work has been shown to work better.
Exactly. For more details, go to the source: Carol Dweck. A good starting point is her popular book Mindset. (www.mindsetonline.com) There's also now online growth mindset instruction for middle school students (and older) -- see www.brainology.us.
