My dd 12 has just told me he is being moved from set 2 to set 3 in science. I'm disappointed, but I don't know if this is normal nowadays?
When I was at school I was in the top set all the way through and I can't recall anyone being moved up or down.
I feel he has stagnated since he was about 8 tbh, but I'm not the pushy type I haven't made a fuss. I've comforted myself with the fact I went to a crap 1 room primary, where I learn't mostly country dancing 
, but I still did well at school.
He is a shy boy lacking in confidence and to go down and confront school would have been mortifying for him.
Anyway,I suppose I want you all to say 'no worries these days kids flit from set to set and it's better for them than struggling to do work that's too hard for him' (trouble is, I don't think it is too hard for him he's such a clever boy)