The difference between education across the world and USA is that you treat algebra as one subject and therefore don't do it every year. In India, you had to do algebra starting grade 6 all the way to grade 12. The more complex the theory, the later you learn it. Makes sense to have that kind of gradual learning imho.
In a US public school, I was doing very basic algebra— math with variables— in 6th grade, which is around age 11. The class called 'Algebra' in the US school system, which this article references, is a subset of what Algebra actually is on a whole. Very basic algebra before high school (which starts at grade 9, or age 14/15) is often called pre-algebra.
In Canada, ninth grade was around 14-15 years old, depending on the month you were born. I think the US has a similar timescale for primary/secondary schooling.
