Have you tried giving him more challenging problems based on his existing math level? Work on his problem solving skills could benefit him a lot. Most high school math is just repeating the example solution with different numbers.

One nice source of challenging problems is the past contest page of the CEMC [1] (disclosure: my university runs these contests and I have participated in grading for them). They have contests for a variety of grade levels and both the contest PDFs and the full solutions are available for download, entirely for free!

[1] https://www.cemc.uwaterloo.ca/contests/past_contests.html

He's doing well in the MOEMS Math Olympiad stuff and is going to be taking a class on inductive and deductive reasoning this summer.

To some extent, we have a different problem-- a lot of what "more challenging problems" tend to be is word problems with lots of distractors and often even vocabulary he doesn't know yet. He has great math intuition and ability to symbolically manipulate and spatially visualize problems, but he reads like a smart 10 year old, not a 13 year old.

I'm sort of assuming this will sort itself out as he gets older-- and he still got an A- in his pre-algebra class (which had enough shuffling of radicals, etc, that it was pretty decent fraction of Alg I).

(Also a little gripe about the online math class having a nominal 3 hour final... you can see his accuracy in the last half of the test was a fair bit lower than the first half).

I'm not sure how English is taught at your son's school, but I have the sense that a lot of schools give kids material at grade level. I think this is an unambitious approach. Reading to challenge yourself is the best way to get better, just as solving challenging math problems helps you get better at math.

Admittedly, it's hard if the kid is not interested in what you're getting him to read. I am a bit dismayed at what appears to be a broad decline in fiction reading among boys. I think there needs to be more emphasis on finding books that boys will enjoy reading while also challenging them.

I have two other boys that are much more well-rounded (further ahead in reading, better socially, but a bit less ahead in math).

I agree the decline of reading is a bummer. I read Tolkien pretty young, too, and even moved on to Homer. It's hard to even picture my kids doing this.

On the other hand, there's more high quality literature written explicitly for kids these days (a lot of what was read / is revered as good children's lit of the past is drivel).

Other things you might consider for your precocious son are puzzle and brain teaser books. I used to love doing challenging puzzles. The books by Martin Gardner can be very mathematically rich. I haven’t read them myself but they were recommended to me by a retired high school math teacher who taught the intro to math education class I took. I plan to eventually acquire a large library of these sorts of materials, once I’ve graduated and have more time, money, and space.

Take a look at Calculus Made Easy. It's non-rigorous - it uses infinitesimals without the machinery of non-standard analysis, instead of limits - but it presents the material in a clear and concise way such that just about anyone who can do basic algebra and computations can learn the material and develop an intuition for how calculus works. Once the intimidation factor is gone, they can go back and learn about epsilon-delta etc.