Here's how AP US History became one of the most controversial classes in America

One of the most popular high school courses in America is also one of the most controversial - Advanced Placement US History, known as APUSH.

Across the country, conservative state lawmakers are fighting back against a newly revised course curriculum for APUSH they say is infused with a liberal bias.

Critics of the new guidelines say they aren't patriotic enough and emphasize negative events like slavery and mistreatment of Native Americans.

Advanced Placement, or AP, tests are taken by high school students for potential college credit in a specific subject.

The College Board, which also administers the SAT, debuted the new framework for APUSH in fall 2014.

The revised APUSH curriculum emphasizes "historical thinking skills" such as "chronological reasoning or a rigorous use of evidence," rather than date memorization, as College Board Director of AP Curriculum Lawrence Charap wrote in a column last June.

"In order to foster these skills, the redesigned courses define the content conceptually and give teachers the same freedom to explore topics in depth that college professors enjoy," Charap writes.

This week, the opposition to the new framework began to heat up again after an Oklahoma House of Representatives education committee passed a bill that would cut funding for APUSH classes in the state.

"We don't want our tax dollars going to a test that undermines our history," Republican Dan Fisher, who authored the bill, said during committee debate, according to Reuters.

Additionally, in Georgia, the state House and Senate held a joint meeting to question Trevor Packer, the College Board senior vice president responsible for overseeing the AP.

The vice chairman of Georgia's House Education Committee said the new APUSH curriculum "seems imbued with leftist, identity-group politics," as the local Morris News Service reports.

These objections aren't new. In an article on the changes last summer, Newsweek quoted former APUSH teacher Larry Krieger, who has been leading the fight against College Board's changes:

"As I read through the document, I saw a consistently negative view of American history that highlights oppressors and exploiters," Krieger said on a conference call sponsored by two conservative groups fighting the new APUSH framework. He read quotes from the framework to illustrate his point: "Instead of striving to build a city on a hill, according to the Framework our nation's Founders are portrayed as bigots who 'developed a belief in white superiority' - that's a quote - that was in turn derived from 'a strong belief in British racial and cultural superiority' and that of course led to 'the creation of a rigid racial hierarchy.'"

Adding to the battle, the Republican National Committee passed a resolution over the summer that described the revised curriculum as "a radically revisionist view of American history that emphasizes negative aspects of our nation's history while omitting or minimizing positive aspects." The RNC said the College Board's framework failed to discuss in-depth the Founding Fathers or the Declaration of Independence, and that it omits figures such as Albert Einstein and Rosa Parks.

Packer, the College Board SVP, defended these changes to the Georgia legislature, the Morris News Service reports.

"What we've done with the new framework is attempted to establish a national consensus around what is required for college credit," Packer said. "We've deliberately not set names (of historical figures) into the framework, by and large, because we want teachers to use their states' standards to fill in the names."