One thing to note is that in the US education system they name classes/courses with the names of fields in mathematics. This is quite confusing and annoying. So

One thing to note is that in the US education system they name classes/courses with the names of fields in mathematics. This is quite confusing and annoying. So "Algebra" actually means "The course we called Algebra 1" (there's an Algebra 2 that comes later, also not really about Algebra). The course called Algebra 1 is basically the material the education system has decided to teach at 9th grade. That material comprises various topics, only some of which are Algebraic. Students are typically (at least in my experience) exposed to "Algebra" (symbols, equations) much earlier. Memory is fading but for my kids something like 5th grade. I still have some of their scrawled equations on a white board in my office from back in those days... Edit: they continue this confusion (at least consistently confusing) by calling the 10th grade class "Geometry" even though it's only somewhat about Geometry, and students will have met triangles and obtuse angles and whatnot years earlier. And so on through to "Pre-Calculus" which...you can guess is not much about Calculus, but the stuff they think should be taught before teaching Calculus (very scary).