But mathematics does extend from low to high. The basic contents of classical mathematics are geometry and algebra. The basic content of mathematics is unchanged from junior high school to senior high school. It's just that junior high school math is more difficult. There are several kinds of functions, from one yuan to two or three yuan, from once to n times, from one dimension to two or three dimensions of space, and so on.

But primary school mathematics can't be called mathematics, only arithmetic.

Just like chemistry in junior high school can't be called chemistry, it is common sense in daily life.