What parts of U.S. history should AP students learn?

Every year, about half a million high schoolers take an Advanced Placement American history class as a way to earn college credits.

But there's been a national debate over what parts of American history should be emphasized.

On Thursday, The College Board -- under pressure from conservatives -- changed the guidelines for teaching the course.

Denver students protest new changes to history curriculum

Students might not notice the changes, but AP U.S. history teachers will. Take lessons on westward expansion.

"In the original version, the focus was almost exclusively on the negative impact of western settlement on Native American populations," said historian Jeremy Stern, who helped The College Board craft the revisions. "Including that is obviously essential, but you also want to talk about the point of view of the settlers themselves."

Like beauty, history may be in the eye of the beholder. And what Seton Hall history professor Williamjames Hull Hoffer sees is downright ugly.

"When you change the story to one of pioneering spirit and economic opportunity, it's not just a change in emphasis, it's a lie," Hoffer said. "The new standards have gone completely wrong."

The College Board changed guidance for teachers about what the final exam will cover. New recommended course topics now include "the American ideals of liberty, citizenship and self-governance" and "the productive role of free enterprise."

"Those are Republican National Committee, presidential, Donald Trump talking points," Hoffer said.

Critics had slammed last year's AP course guidance as unpatriotic. Lawmakers in many states went on a rampage, pushing for changes.

In Colorado last September, conservative school board members said the AP American history "materials should not encourage or condone civil disorder." That sparked civil disorder-- massive community protests.

The Republican National Committee adopted a resolution calling last year's framework "biased and inaccurate."

Ben Carson, a Republican now running for president, went even further.

"I think most people, when they finished that course, they'd be ready to go sign up for ISIS," Carson said.

The College Board knows the revised framework won't make everyone happy.

"I think people, frankly on both the left and the right, have greatly exaggerated the power of this document," Stern said.

The College Board doesn't mandate specific textbooks. The framework is a guide, not a requirement, about lesson plans.

AP U.S. history teachers remain free to teach what they think is important, without considering the controversy du jour.