Why does world history class from elementary school through high school only gives brief or no mention at all of the
contributions of the non-western world to the progress of world civilization?

Why do teachers and professors go on and on about the achievements of the Europeans after the Crusaders and Renaisance? What about the Chinese who invented gunpowder and originally used it in fireworks, but we now use today in firearms and other deadly machinary? What of the Moors, Arabs, and Ottomans who built modern day irrigation systems in desert areas and arid lands? Or how they preserved the writings of Ancient Greece and other forgotten texts while parts of Europe were trapped or struggling to escape the Dark Ages?

What about the Chinese strategist Sun Tzu who wrote a manual on using military strageties to defeat an opponent? Why have these and other contributions only been mentioned briefly?

Is it true that history is truly written by the victor?