This is a straight up guess, but the timing is really close: adoption of Common Core?

What I've seen of Common Core math is very different from how it's traditionally taught, to the point that parents don't understand it. I think I can see a thread in there, that it's attempting to teach what those of us good at math end up figuring out ourselves with numbers, but the examples online are bad and lead to further misunderstandings. So I could see teachers having similar issues, and students not learning very well because of it.

To put it in more techy terms, Common Core math is like learning computer science before learning your first programming language: probably possible, but it won't work well for most people.

I'm not sure what the Common Core curriculum for reading is, although on the whole Common Core math curriculum, it's a good system. You're right that often parents don't understand that—but that's due to Americans on the whole being uncomfortable and unskilled in mathematics. It does require teacher education, however, and lots of places are cutting that back.