Yes reading a lot is helpful, it will help to build his proficiency for when he gets to college. Documentaries are helpful as well, they offer more engaging ways of learning about history. Once your kid finds something interesting in these documentaries he can read about it to gain the bigger picture. When I was a kid, my dad watched a lot of documentaries and that’s how I gained my interests and focused my efforts. Also another way I was able to develop when I was a kid was by joining my local historical society, there was one for ages 8-21 where I’m from and they get together about once a week and talk about history, visit historical sites and archives, etc. it’s also helpful to check what events are going on at your local museum as well. I hope this helps.

When I was his age, the books that more than anything helped to cultivate my love of history was the Cartoon History of the Universe series by Larry Gonick, and I really can't recommend them highly enough for a kid who thinks history is cool. I still have all the books, and the sheer tatters that the early volumes are now I think speak to how many times I read through them.

I would add a few words of warning though. They aren't kids books. They are definitely kid friendly, but they do have mature topics. I don't want to presume what you consider proper bounds for your kid - my parents either didn't realize or didn't mind - but there is sex, violence, and 'adult' topics throughout, so do make sure to preview through them and make sure you are OK with giving them to him!

Now as for the history itself, I would never recommend the series as a serious source of history that you should cite on the sub, but it is the kind of thing that I'm willing to make concessions on. Especially for younger audiences, cutting some corners is really fine in my opinion.... hook them first, and worry about correcting those errors when they are a bit older and can handle the more granular texts. And as for what those 'cut corners' are, they fall into three groups.

Some of it is just a reflection of outdated scholarship. The first volumes were published in the '70s/'80s, and will reflect that at points. Comparing the final few volumes to the earliest ones, even a general knowledge of the topics, you can see how the latter ones simply reflect that they were written, well... later!

The second is the medium itself. It is, essentially, pop history, and communicated via a highly visual style, which means there really isn't much ability to get too complex in the text. Gonick for the most part does the best he can within those limitations, but it obviously is something to keep in mind.

Finally, there are definitely points where it is wrong, although this in part intermixes with the earlier two. The one that I definitely remember is engaging with Gavin Menzies 1421. I don't recall if Gonick takes it as definite, but he does at least imply the Chinese might have reached the West Coast of the USA in the 15th c. which is roundly dismissed by the academy. I know there are a few other examples, but that is the one I can recall immediately.

Still though, despite those words of caution, I still am a huge fan, and I really am quite serious in saying that there is no single thing which is more responsible for my lifelong love os history, and at that age range, I really think that between the accuracy is a little less important on the scale versus building up that love and excitement. Getting through that first step means the later ones are going to be pretty easy to ensure happen anyways.

As everyone else has said, read, read some more, and when you’re done with that, go read a bit more.

I love the primary source research suggestions. Ask your library if they have a local history archive you can visit or if there’s a local museum with one. If you live near a college or university, they may also have an archive. The one caveat with college/university archives is that the collections will vary. Some may be strictly limited to the institution’s internal paperwork while others may have really fascinating stuff. My guess is that any small to mid-sized institution/library/museum you reach out to, they’re going to fall all over themselves to engage with your son.

Some other posters have pointed to this but I want to say it explicitly, develop his critical thinking and information literacy skills. IMHO, all parents should work on this with their kids but it sounds like your son is pretty intelligent and will be going places. Helping him learn these skills now will benefit him immensely no matter what he goes into but especially if he goes into history.

A final thought- at his age, I would have LOVED to be involved with a local history organization. They could have had me stuff envelopes or sweep the floor and I’d have felt like the Queen. Maybe when the pandemic is over, he can get involved in some history related volunteer work?

I'd do some primary source research with them. See if your local library has access to Ancestry or other genealogical resources and have your child research the family tree. One of the things that really got me interested in the field was an assignment in 7th grade to pick a tombstone of someone who lived during the time of the American Civil War and write a paper about their life. I used census data, vital statistics records, newspapers, and military service records to find information.

Everyone's got such great suggestions and I wholeheartedly endorse the historical organization suggestion from u/auditorygraffiti. I used to volunteer at a local museum and it was so wonderful to see the kids get a spark in their eye when they saw how "real" history can be outside of a classroom.

It sounds like you are already planning some historic travel, which is an awesome idea, and I would encourage your son to help plan these trips as well as set some bigger historic travel goals. If he's interested in English history, maybe ask him to help plan a post Covid UK history trip? Or something closer to home like a Colonial Williamsburg or historic Boston trip? Even if it's not happening in the next year or so, a lot of people's introduction to history is through travel and it's a great way to set a long term goal that can be as academic as he wants it to be and give him a lot of control over the process. Whatever you do, I'm sure it's going to be a blast for you both!

You could maybe look at the British Newspaper Archive website with him? They have hundreds of years of papers and there’s lots of interesting stuff in there from when events were happening like WWII, etc - if WWII and British history are his interests it could be an interesting way to view primary sources and research events himself