Thanks all so much for you ideas. I've only got a minute so I can't respond properly for now, though I will take a second to mention that, Edwin, I couldn't agree more - but we do absolutely only praise effort. One problem is, as HowlerKarma suggests, that she gets plenty of praise for being smart elsewhere. Though I do sometimes wonder if dh and I have gone over board praising effort and ignoring the smart bit and so she doesn't 'feel' smart when people tell her she is. Or something. Plan to have a more in depth chat about learning vs knowing too.
Thanks again.
