Short version: there has been a continuous effort on the part of western colonial powers to marginalize the histories of the people of Africa, South America, and the like. 1492 and 1493 by Charles Mann are great histories of the Americas with a global dimension. For books on how and why these histories have been marginalized I recommend Edward Said, Aime Caesaire, and Albert Memi.

Edit: long version Why aren't these histories taught in schools? Typical general history courses in the United States tend to cover world history starting with the birth of civilization in Mesopotamia and devote most ancient histories to that of Greece and Rome- proceeding into the rise of Christianity, fall of Rome and the medieval age, onto perhaps the Crusades and then Renaissance, Enlightenment, Industrial Revolution, Western colonialism, world wars and so forth. Notably absent are the histories of Africa, Asia, the Middle East and the Americas. Essentially the modern historiography that you refer to relates to how Western Europeans saw themselves and saw the rest of the world during their heydays. They depicted their own civilizations as being the inheritors of the ancient civilizations of Greece and Rome- the western civilizations.

In order to understand why your typical western historical outlook lacks an African or Asian vantage point you have to understand the concept of orientalism, as outlined by Edward Said. Essentially Europeans romanticized a vision of the east as an exotic place of wealth and splendor, basing this preconceptions on past civilizations such as the Abbasid Caliphate or those of imperial china. What they saw when they began expanding and colonizing was that many of these civilizations were in decline and their preconceptions were misplaced. Combine this with emerging racism and notions such as the white mans burden and we see European powers modeling themselves as the civilized versus the savage, primitive backwards people of Africa, Asia, and the Americas. To what degree you can call the efforts of historians to marginalize the histories of the third world is up to debate, but it is clear that in order to support and justify their continued superiority over their colonized peoples they had to paint history in such a way that flattered them. As many of the former colonies moved towards independence, colonized peoples made an effort to reclaim their historical legacies and assert their independence: thinkers such as Fanon and Memmi went to great lengths to express these ideas in works such as Wretched of the Earth and the Colonizer and the Colonized.

Again, to what degree this was a malicious effort is difficult to ascertain: the individuals who write high school world history textbooks probably don't have an evil agenda ( or do they?!) but they have inherited a historiographical tradition that goes back centuries.