Math is amazing in that there is a very clear learning path from 6 years old until a Math Ph.D. qualification exam, with everything in between.
So when you start to help a kid who loves math, do more math, it is very easy to start accelerating your kid down the math path from arithmetic to Calculus and beyond.
If you’re not familiar with it, it’s basically arithmetic all the way to pre-algebra, then algebra, geometry, algebra II, trigonometry, pre-calculus, and then calculus. You can more in-depth information about the USA’s Common Core State Standards for Mathematics (PDF, Nov 2022) in the linked document.
This works great until the kid starts to get too far ahead of the school and then your kid runs into a bunch of related problems: