High school world history is essentially "mainstream" history; the principle path of key events leading to the modern world. While this does a decent job of explaining the overview, many of the most interesting matters are ignored.
Some textbook authors might see themselves as doing students a favor by not producing a deluge of names, dates, and battles. This can be unsatisfactory for it often fails to place things in context (I am not so modest, so get your waders ready). If we mention that during the Civil War, both sides used the Napoleon cannon, we should also mention it was named after Napoleon III who was ruling France at that time, instead of allowing students to think Lee and Grant were using fifty-year old field guns.
The rise and expansion of Islam has to be considered more significant (both then and now) than the development of feudalism in Europe, but such matters usually receives little mention.
History books usually mention the Ottoman Turks capturing Constantinople and conquest of the Balkans, but omit their taking Mesopotamia away from Persia, the long-term result of which is the nation of Iraq.
From these two examples it would seem history books are not terribly interested in currently applicable historical lessons.
Also some of the more interesting people are ignored. While the relatively uninteresting, if ill-fated, Constantine VII will be mentioned, how many history books mention the problems the Turks faced a few years later against that steadfast opponent, Vlad III of Walachia? Besides being a strict disciplinarian and clever tactician, Vlad became once again relevant in the late 1800s when Irish writer Bram Stoker borrowed his nickname as the title character in his novel Dracula.
And there are also times textbooks skimp on details. A great example, and principal topic of this piece, involves the English king, Henry VIII. Some will mention that Henry's older brother, Arthur, died young, and Henry married his widow, a woman called Katherine of Aragon. They will also mention that the Pope refused Henry's request for an annulment when Katherine seemed unable to give birth to a son.
Here the story ends in most textbooks, leaving the students to guess for themselves why the Pope turned down Henry's request. Most will figure the Pope was a prude who felt that marriage was indeed "til death do up part".
This is not at all true. Royal marriages, and producing an heir, were big things back then, and a Pope would have granted the annulment in most cases. But this was not most cases.
At the time, the Holy Roman Emperor, Charles V was the most powerful man in Europe; the Pope was deathly afraid of him, and Henry's wife just happened to be his Aunt Katherine (who would have been dishonored by the annulment).
Charles was a rather interesting character in his own right; he was born in 1500, the son of Hapsburg prince Philip the Handsome and Spanish Princess Joanna the Mad (daughter of Columbus' patron Queen Isabella).
Charles and Pope Clement VII had a history of animosity. In 1519, Holy Roman Emperor Maximilian I died. Under the system used at the time, the new Emperor was selected by a group of key German nobles, called Electors. As every past Emperor since 1452 had been a member of the Hapsburg family(Maximilian being Charles' grandfather), the young prince was in an excellent position to be elected.
But Clement realized that if this were to happen, Charles would control virtually all of Christendom between France and Poland, plus Spain, and Spain's growing New Wold empire. Hoping to improve the balance of power, Clement supported France's ambitious young king Francis I in his bid to become Emperor.
Charles, however, was able to bribe the Electors and secure the position. The troubles between Charles and the Pope continued until 1527 when Charles successfully besieged Rome. What followed were three days of pillage, rape, and murder by Charles's army. While embarrassed by the carnage, Charles was not displeased, knowing it sent a lasting message to the Pope not to meddle in Imperial affairs.
So now you have poor Pope Clement, an Imperial prisoner, the horror of the bloodshed still fresh in his mind, and now receiving Henry's request for annulment. There was no way Clement was going to piss off Charles by granting the request.
So Henry (actually not at all a fan of the Protestant Reformation) breaks away from Rome and starts the Church of England. He then divorces Katherine, and has five more wives (only one of whom would provide him with a son, and only two wives who were beheaded). His first two children to rule (Edward VI and Mary I) would both die young, causing later speculation that Henry suffered from syphilis. But his younger daughter, Elizabeth I, would rule for nearly 45 years and give England something of a golden age.
Clement VII would die a few years later, and be replaced by Paul III, who is best known for helping start the counter-reformation, and for making his sons cardinals.
For all his dash and ambition, Francis I's reign as King of France was something of a disappointment. He was known as a patron of the arts. But his military career was far less grand, culminating in the Battle of Pavia in 1525 in which in which he was captured by Imperial troops. He was also noteworthy for being the first Christian monarch to enter into diplomatic talks with the Ottoman Empire (enemy of the Holy Roman Empire).
Eventually the stresses of ruling such a vast empire proved to much for Charles. He retired to a monastery in 1556, dividing his empire between his brother Maximilian, who received his Austrian possessions (and would be elected Emperor as Maximilian II), and his son Philip, who got Spain, the low countries (modern Belgium, Luxembourg, and the Netherlands), and the Spanish New World. Charles would die two years later at the age of 58.
While the need for brevity and succinctness in textbooks makes including such a complicated story unlikely, I have some suspicions there might be one other reason this story goes untold. To go into Charles' election as Emperor, one would have to mention that in order to bribe the electors, Charles had to get a huge loan from a wealthy German banker named Jacob Fugger ... and no high school teacher wants to say that name.