It's obviously an individual situation, but neither had issues, and I view Math as a bit different than many of the other subjects. It's so factual/concrete that maturity levels, age differences, etc., aren't that meaningful.
While I don't expect the OP's child to have any problem with algebra, I think this may be going a bit far. There's an abstraction level in algebra 1 that I think you have to be developmentally ready for, just like you have to be developmentally ready to learn to read.
Agreed.
That said, and going off on a tangent, today's books are much less abstract than they were up until about ~25 years ago, with the decline starting in the 80s or so. I have old high school math books that are breathtakingly abstract.
Modern Introductory Analysis (1964) is a good example of a deep, proof-heavy book. A newer edition called
Introductory Analysis was published in the late 1980s and is much less proof-heavy than the first book.
I have a 46-page booklet called
The Complex numbers (1965) that's supposedly aimed at high school students through interested adults. It contains a proof that took two pages to develop.
Today, math education is way more concretely focused than it used to be. I understand the need to apply math to solve problems, but think that the drastic loss of the theoretical stuff is a problem ---there's a lot to be gained from grinding out some proofs. And the old books also had a lot computation.
To the point about readiness for algebra, I used to present my kids with algebra-like problems to gauge their readiness. I'd see signals indicating readiness or not. In particular, before they were ready, they wouldn't retain what I'd taught them. Now, it's normal to forget stuff --- especially when you're learning a lot at once, but it was different when they weren't ready. I'd have to re-explain everything all over again next time, and there was basically almost no memory of the previous round. It was also extremely difficult for them to apply ideas before they were ready.
I once overheard a conversation about reading with the same conclusion: "I've been teaching him for almost a year, and he hasn't really improved." "Yes, me too."
