Oh, I really don't like when teachers respond like that.
Just to give an update on DS (almost 6): today is his second day full time in first. HE LOVES IT. He was thanking us for helping him to get to first. He feels like he is doing more challenging things (still way bellow his capabilities, but it is a huge step up from K in his eyes). He feels like he can relate more to the children in first. But his favorite time still is when he gets pulled out and is doing math with gifted 3rd graders.
So, as of now. I think he is where he should be, I am really happy that he was skipped into first.(Although, our first thoughts were that one year will not make a difference, and were not ready to move him more than one. But now I see that even the one year makes a difference.)
To him everything is new, classroom, friends, rules, etc. I hope, for awhile, his brain will be busy with that. And we see, what we do in the future, taking it day by day.