My DS is 7 and in year 3, he has just moved up to a new school (junior school) which is linked to his infant school.
They have introduced the "growth mindset" thing a year or so ago and I'm fine with that; however at the new school I'm not sure they're selling it right. Let me try to explain.
DS is bright and naturally academic and usually needs a bit more of a challenge at school. I asked him how it's going, what they are doing in Maths. He told me what they had been doing that day and that it was all a bit easy. So I asked if he had told the teacher this and maybe got something more challenging to work on. He became very uncomfortable and said no, because "if I find things easy that means I haven't got a growth mindset". He was upset about this as he strives to do things right, and in his opinion finding things easy is the wrong thing to do 
So a few days later I asked him again about school, and he explained to me that in order to learn you have to "fall into the learning pit" first (i.e. Not be able to do something) and then "work hard" to get out of it; and if you are able to do something straight away again that's "wrong" and means you're not learning?!
I find it worrying that DS now thinks there's something wrong with him or being able to grasp new concepts quickly. Surely the school can't mean to convey that this is so, but it seems that is what they tell the children?! I've chatted to another parent, whose daughter is also very bright, and she has reported a similar story from her DD.
I guess my question is, do I seek to speak with the teacher now (maybe just to clarify what's going on and how they word this at school), or am I making too big a deal and wait until parents' evening (November)?
On a side note, the work they do at school does seem to be really easy for year 3 and there seems to be no differentiation. DS has had two maths homeworks so far and they both were variations of "find the biggest number" - one was just a line of 5 numbers which had to be sorted from smallest to biggest! They are also learning to "count in 4s and 8s" when my DS is very confident with his times tables up to 12x.