What was the general level of historical education of watchers of Shakespears plays? Would a average watcher of the history plays (Richard III, Henry V, etc) know what had happened in general terms before watching them?

This is a super fun question! My area of expertise is Shakespeare, so I'm gonna hop in. As always, my disclaimer is that there are tons of people who have far more narrow fields of study, but I'm going to approach this from sort of a dramaturgical and historical standpoint. Like always, sorry for how long this is.

The first thing to keep in mind is that while Shakespeare based his plays on historical people/places/things, they are, at their core, dramatic interpretations. The history plays, in particular, take liberties with historical facts and insert characters sometimes years before they were actually born, or, in other cases, some that never even existed. He expands and compresses time at will (sorry not sorry for the pun). Events that took years take moments, births and deaths jump years. For Shakespeare, the important part was telling the story.

Now let's talk about Star Wars. Since it was first released in 1977, Star Wars has become a part of the collective consciousness. Even if you've never seen the movie or have ANY idea about the plot, you probably know that Luke Skywalker has a sword that goes FWOOOOMMMMM and Darth Vader is a tall black robot man and you've probably heard the phrase "may the force be with you". Keep this in mind, it gets important later on.

The dates in which Shakespeare worked on certain projects is always up for debate, but we know he wrote almost all of the histories early in his career, most likely around 1590-1598 or so. What's interesting is that this was...pretty trendy. Just like we have the Avengers Infinity War cycle today, early modern playwrights of the time wrote "chronicle" plays that told stories of different English monarchs, so this wasn't a particularly new invention-- playgoers would have been used to this type of entertainment.

However, we, the audience watching Henry VIII 2018 has a very different view than people who might be sharing a theatre with Queen Elizabeth I. No pressure, right?

Your question was not about whether or not Shakespeare got the history right, so I won't go too far down that rabbit hole, but if you're interested in learning more, Dan Jones wrote a really easy-read article related to this topic awhile ago that I highly recommend.

So. You're an audience member in 159something watching Henry VI part 3 (I'm so sorry, should have waited for Henry V). What do you know? Do you know who these people are? It is exceptionally hard to paint a broad picture of cultural knowledge without being terribly assumptive in some aspects. I've answered on AskHistorians before about education during Shakespeare's time, but the playhouses were historically a melting pot of people from all walks of life.

In "Shakespeare's Audience", Alfred Harbage estimates that The Globe Theatre held around 2,500 and further postulates that the average daily attendance in 1595 was 1,250 audience members and that " 160,000 people lived within walking distance of the playhouses, and 2 of every 15 people living in London went once a week to the playhouse". That is a large swath of the population. (Honestly, just read his book, it's FANTASTICALLY interesting)

We know that the playhouses were close to some of the law schools in London, and we also know that much of the London population was made up of merchants and apprentices, so the literate audience was probably higher than many people assume, but there were also lots of people in London who couldn't read.

If you could read, and you had the money to afford books, there were several "history" books that had been published in the fifty or so years prior to Shakespeare writing his histories. Holinshed’s Chronicles of England, Scotland and Ireland (1577) is one of the biggest known sources for most of the histories, along with influences from Edward Hall’s The Union of the Two Noble and Illustrious Families of Lancaster and York (1548). So records/books existed, and we can argue pretty solidly that Shakespeare read these books-- it stands to reason that some of his audience would have had access to them too.

Academically, we know that history wasn't a taught course in grammar schools like it is today, but there were scholars and lawyers tasked with tracking the lineage of the ruling monarch to make sure everything was on the up and up, so some care had to be taken to avoid being overtly treasonous while writing his plays.

So here comes the longer, more dramatically-oriented answer. Remember when we talked about Star Wars earlier? the thing that I (caveat, this is just my opinion as an informed scholar) think is most interesting is that we can track a lot of historical knowledge through things like songs, plays and ballads. Rather than have history class, people used the oral tradition of performance to tell their history. In fact, some writers of the time even praised the playhouses, saying that anyone who attended the theatre " sharpens his wits with frequenting the company of Poets " (Thomas Nashe, around 1592), so there may be something to the argument that people may have actually used this history plays as a sort of education-- sort of the reverse of your original question.

Figures like Henry V who saved all of England, or Henry VIII who nailed six chicks and all he got was his own religion or the already less-than-flattering version of Richard III --- all of these, just like Han Solo and that weird furry bear dog he travels with were already in the cultural consciousness. However, just like not everyone on the street knows who Salacious B. Crumb is, Shakespeare fundamentally understood that you, as the audience, might not automatically remember where the Earl of Salisbury falls in the line of succession or why he matters to the Lancastrian claim to the throne.

Shakespeare was also a theatre person. He worked in the playhouse as a writer and an actor. He knew his audience. I think he probably loved the London audience because he recognized how many different types of people came to see his shows. He understood that to keep your interest as an audience member, he had to combat not only the conditions of seeing a play in the playhouse, but also allow you to follow the plot, so he provides a lot of background and moment-to-moment clues. This is the reason why people come on stage all the time and say things like "Ah, my lord Cousin Exeter" (or whatever). Shakespeare clues his audience into the important facts-- relationships, status, etc. (Luke, I am your father...) to help everyone along.

I think you can, in looking at the history plays, pretty solidly argue that Shakespeare assumed that his audience had a broad understanding of who the major players were, but, based on the textual evidence mentioned above, he didn't assume they would know -- or remember everything.I hope this was helpful! Please let me know if you have any follow-up questions.

Bibliography/Further Reading

Becker, George Joseph. Shakespeare's Histories. Ungar, 1977

Bevington, David M. Shakespeare's Histories. Pearson Longman, 2007.

Clegg, Cyndia Susan. Shakespeare's Reading Audiences: Early Modern Books and Audience Interpretation. Cambridge University Press, 2017.

Finley, E. E. Shakespeare's Audiences. 1917.

Edits: Formatting and spelling because I'm a scholar, not an editor.