Given that the amount of history we record is (basically) exponential and schools only have limited amount of time, how should they decide what's important enough to teach? Is something like the Louisiana Purchase important enough? In the future will schools be forced to offer a cliff notes version of everything history, since the source material will be so large?

This problem doesn't really occur with other disciplines such as mathematics, since it builds upon earlier classes, reducing the flexibility in subject material.

It depends on what type of history is being taught. If the class is US History, then yes the Louisiana Purchase needs to be taught.

The problem I see is in the teaching of "World History". This is a large all encompassing survey course and vital things can be left out depending on cirriculum standards and the views of the administration.

An excellent question, one that I'm forced to grapple with constantly as someone who teaches survey courses.

The main thing I do is pick out a couple of major themes I want to cover for the term, and then try and select examples that will function as a narrative for these themes. For instance, in early American History, I often try to emphasize the struggle between State and federal power in the early 1800s, and explore the differences between the idealism of the so-called "Founding Fathers" with the political demands of the time--as it happens, the Louisiana Purchase is a great example of both of these themes and illustrates the conflicts with the Jefferson administration.

It's much tougher for World Civ--thus my themes have to be chosen carefully. For Ancient/Medieval World Civ I focus on the conditions necessary to create a "civilization," the factors that go into the "fall" of a civilization, and the formation of some of the great world religious and philosophical systems as a lens for seeing social change. For Early Modern Civ, I basically encourage students to reflect on a question: "How and why did Europe--a cultural backwater in 1400--manage to conquer the rest of the globe by 1900?" For Modern Civ, I try to explore the various facets of what we mean by "globalization."

Different instructors tend to structure their courses in slightly different ways, but there are usually some events that are so important that they fall into the narratives regardless.

This is all survey courses ever are anyway: Cliff's Notes. The best you can hope for is to expose students to some of the major trends, how historical research is done, and how to analyze historical events. If they're really interested, then you point them to areas of specialization. But I always tell students, even if they take a year's worth of my survey course, they've only really scratched the surface.

Required historical learning should increase the higher up the IQ scale you go. The more your future requires you think, studying past decisions takes on more importance. Law, business, politics, research, etc are all well-served with in depth study of particular events.

The survey class on American and Western Civ is in decline, in popularity and usefulness. There is no symbiosis with culture and identity on a national level to supplement it. So many hs and college kids show up not knowing more than a Mel Gibson movie about history. Or worse, tea party signs. Unless hs education fundamentally reshapes itself around teaching analysis and writing over four years AROUND civics and history, history education will return to the pervue of the elite. One of my friends teaches a survey US history class at a mid-low tier public uni and I read his kids' papers and exams. They show up with no knowledge or cultural memory, whatsoever.

If you have a promising pupil, push him to the better popular histories and biographies, or classics(Thucydides, gibbon, Herodotus, roman authors). If you have the time try to get a handful of the best to read together. If they prove they read and think, lighten there class work burden and inflate the grade, because the more they read, you've done a better job. Jesus, if just one starts to think, it's time for hookers and blow.

6-10th grade social studies/world history/civics is a multicultural, multidisciplinary, incoherent pile oh horse****, no one learns or retains.