FWIW, I never studied anything beyond World War II in any elementary, middle or high school history class I ever took. There was never enough time in the school year to get further than that. I distinctly remember that in my 8th grade American history class, we started talking about World War I the last day of class before the final and our teacher said there wouldn't be anything about WWI on the final for that reason. He also claimed we were the worst class he ever had and that our counterproductive, off-topic behavior was the reason we only made it up to 1915-ish.
Unfortunately, this is a huge problem pretty much everywhere. As a crappy solution, Tennessee and Mississippi (maybe other states too, I don't know that much about every state's curriculum) do only through 1877 in 8th grade and then only do 1877-Present in high school US History. It's not much better.