Thanks everyone. My wife and I actually had a parent-teacher conference this afternoon, and I was quire surprised when the teacher told us that math is the one area where our daughter struggles a bit. She told us that they gave our daughter 7 blue blocks and 3 pink blocks. Our daughter had no problem saying which pile had more blocks, but became confused when asked how many more blocks were in the bigger pile. When we got home, I asked our daughter how much 7 minus 3 equaled. She let out a huge sigh and said "too easy, 4".
The teacher also said that our daughter was also having some difficulty with something called number bonds, and showed us a sheet she had completed in class. A number bond seems to be a number in a box on top with 2 circles below, one of which also contains a number. The student is supposed to fill in the missing number, such that the numbers in the 2 circles equal the number in the box. I printed some out from an internet site and gave one to my daughter when we got home, and immediately saw the problem. She was adding the 2 numbers shown and putting the total in the empty circle. When I showed her how to do it properly, she had no problems at all, even when I added a third number into the bond.
All in all, I think the problem is with common core, and not with my daughter's math ability.
In any event, I asked the same question I posed above to my daughter's teacher, and she said to feel free to teach math to my daughter any way I see fit. The objective of common core, she said, is to teach kids multiple ways to get to the answer, so one more way should help. The teacher also added that she agrees with the CC objectives, but doesn't like the way it's been implemented.
