I was talking to a friend this week and she was confused by her 5th graders math. It wasn't that she didn't understand the math, she didn't understand the vocabulary that her 5th grader was using and therefore couldn't help her.
Math has changed. Well the math hasn't changed, the words teachers are using to teach kids math had changed. No longer do we call 3 a number, it's a digit, we no longer "borrow from our neighbor" we "regroup". This can become frustrating for the child and the parent. There are also some weird looking methods to do math like the Lattice Multiplication method. Schools have moved this way to better prepare kids for the math language. So later on in life they won't need to re-learn that 364 is made up of the digits 3 6 and 4.