Here's the thing. Many elementary ed.-level teachers in the US just don't understand math. Given this fact, they're heavily dependent on what the book says as a way of assessing your child's knowledge. So say the school's first grade math book shows 3 methods of doing addition (say, counting things that you combined, jumping forward on a grid or a number line, and a rule-in-rule-out algorithm).*
Now say that your child gets the Common Core "addition means combining things" idea intuitively. If the teacher doesn't honestly understand that those 3 EM methods are just different ways of showing this one concept, she might decide that your son's understanding of addition is incomplete. She might especially feel that way if he starts getting frustrated with rule-in-rule-out. To the HG+ kid, it's lame. To the teacher, it's critically important because the book said so. The book was written by experts!
So true Val, I couldn't have written this better.
