Most American schoolkids learn that in 1492, Columbus sailed the ocean blue – but what about the Mayans, the ancient Egyptians, the Chinese dynasties or the other great cultures that thrived long before the Italian explorer set sail for North America?

That vast sweep of earlier civilization could remain a mystery for thousands of high school students taking the Advanced Placement, or AP, World History course offered through the College Board, under a controversial change to its curriculum and the AP exam now slated to take effect in the 2019-20 school year.

The College Board said the current iteration of AP World History crams way too much information by trying to cover thousands of years of civilization in nine months – especially with many schools offering the class primarily to 10th graders who've not taken a college-level curriculum before.

But its plan announced in June to expand the course over two years  and test students only on history after 1450 has sparked such an uproar that the board is already likely to vote this month on an alteration that would start the test material at least a couple of centuries earlier.

That revision probably won't satisfy many history teachers and students who are riled by the 1450 cutoff because it means the future class would focus heavily on European culture and ignore the contributions from earlier, move diverse societies in Asia, Africa or the Middle East.

"They're cutting out early civilizations and their interconnectedness, cutting out a lot of really neat stuff," complained Steve Smith, a veteran history teacher at Downingtown East High School who's been teaching AP World History for three years. "They're cutting out the Silk Road trade, not just the exchange of commodities, but religions like Buddhism, Islam, Christianity" – and missing other big developments from before Europeans began colonizing the world.

The defenders of keeping the AP World History curriculum and test as it is acknowledge the current iteration covers a lot of ground but argue that so do other difficult subjects like biology – and you wouldn't teach the human body from only the waist up.

What's more, the debate taps into broader anxieties that in a time of fraught international relations and rising concerns about intolerance, American kids simply don't learn enough about the contributions and values of the world's many diverse cultures.

Merry Weisner-Hanks, the president of the World History Association who had played a key role in developing both the current AP course and its exam, said the primary goal was "to talk about the shared history of humanity from the beginning — the Paleolithic past. What did it mean when people started to raise crops, invent religions? What happened when people started to live in cities?"

"Part of the current political moment," she added, "is completely short-sighted about many things people have been doing for a really long time."

Officials at the College Board said the reason for making the change wasn't to disrespect ancient cultures but because it concluded that one school year simply wasn't enough time to teach the entire scope of world history to 15-year-olds. They said a survey of history teachers showed a majority thought the 100 centuries of humankind covered by the current curriculum is too much material, while students posted low scores on some essay sections of the AP exam.

The changes recently announced by the organization aim to convert AP World History into a two-year course, with an initial year that would cover the period from about 600 B.C. to 1450. But the AP exam would cover only the second year that is based on world history after 1450, and teachers and other educators said the likely impact is that most schools would offer only that second year.

Jaslee Carayol, the College Board's associate director of media relations, said of the two-year approach that "we are following the same model that colleges use, and that we have used for most other AP courses, whether in science, English, mathematics, world languages, or the arts, providing students with a foundational year of content prior to the AP year."

"However, since announcing the two-year program last month, we've been moved by – and completely understand – the concerns on behalf of students of world history," Carayol said. "We recognize how important it is for students to study non-European cultures and civilizations prior to 1450; we will address such principled concerns in a revised approach we will share soon."

Weisner-Hanks said there was a considerable dissention over the change at last month's annual convention of the World History Association in Milwaukee, where critics said that the College Board hadn't consulted with educators before announcing the move and that "this goes against everything in the field." She said low scores on the essay portion of the test occurred because most schools slot the difficult course for 10th graders.

One 15-year-old who just completed the course, Dylan Black of Tinton Falls, N.J., was so disappointed to learn of the pending changes that he launched a petition drive on urging the College Board to reconsider. He said "I understand the logic" behind simplifying AP World History, but said that it makes little sense to start it during the Renaissance in Europe without learning the trends that preceded and inspired it.

"It completely changed my view on the world around me," Dylan said of the class. "I had some historical knowledge from social studies in middle school, but now I look at things and can see why they occur."

Stephanie Skoglund, who teaches AP World History at Downingtown West High School, said students in the Chester County district have generally done well and earned their AP credit after taking the exam. She said the College Board is "putting too much emphasis on the test rather than the growth that [students] get."

"They're doing a disservice to the students by not allowing them to learn about the diverse histories and cultures in Asia, South Asia and Africa, and the Middle East," added Skoglund, who also teaches a non-AP required course on Eastern Civilization. "The whole region that is so important to our world today — to not know about those places and what they were doing prior to European exploration is not great."