That's not the way I learned it!! Edit Added
As a parent do you expect your learn things the exact same way you did when you were in school?
One of the hardest things to deal with as a teacher is when parents don't support the teacher's instructional methods. When kids go home and hear, "That's ridiculous. Don't do it that way, do it this way!" It totally undermines what we do in class all day.
Instructional practices are changing and will continue to change. Education is a field driven by research. Scientists are learning more about how the brain works. And educators are always looking closely to determine what teaching practices are most beneficial for what kinds of learners.
Maybe the way you learned worked great for you. But that doesn't mean it worked for everyone. Maybe the way you learned worked OK for you. But that doesn't mean other approaches wouldn't have been better.
Either way, if you don't value the training, knowledge, expertise, and experience your child teacher has to offer it's an issue. When something is unfamiliar try not to immediately assume it's horrible. Consider the fact that teachers spend years learning how kids learn. So maybe the teacher knows something you don't know.
This seems to have turned into a math post. LOL Which is interested because lots of things have changed other than math. I think it's the math homework that makes it so obvious.
Something to consider is that students in the US are very behind their peers in other countries when it comes to math. As we up the standards for this generation to catch them up to other countries it's obviously going to seem much harder than we did growing up. But the average American parent's math skills are not what we're striving for with our current students. So yes, the math your child is bringing home is hard for you. It's probably also hard for the teacher. You and the teacher had much lower expectations growing than students do now.
Basically, what was once considering mastery level of basic math skills is now really just a basic understanding. When we were growing up that was fine. But that's why there are so few Americans in engineering, science, and other math related fields. The local university offered 30 grants to doctoral candidates for an engineering program. One native US citizen applied for one of the spots. None of the professors involved were born in the US. The American education system just hasn't been providing the strong math/science foundation needed for many fields.