Algebra? No idea. I learned it at 11. I’d think at least anyone with an average IQ should be able to manage basic algebra. I mean, if you can handle fractions you can handle basic algebra concepts. Algebra is hardly esoteric knowledge. It doesn’t even require a calculator.
In my state, it's required for graduation.
Of course, my father said it was required for graduation in his school 50+ years ago, too...