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.
I am personally a great fan of chronology, but history education doesn't have to be chronological. Often you can start with current affairs - like when you take Islamic terrorism or Islamophobia in Europe and work your way backwards to the crusades and look at how Christians and Muslims have interacted and the resulting conflicts. I think that approachn is preferable on a lot of issues when you are teaching teenagers, generally you get more motivated students (the ones that can be motivated ...) if you start with current affairs and try to put them into historical perspective. US history is well suite for that approach.
Historical knowledge is generally pretty useless if you don't use it to think about how the world became what it is today. So critical thinking is at the core of studying history.
