The key is that students have to begin early, or, if they don’t, they have to go back and begin with the fundamentals. Math skills and concepts that students learn in high school are built on those from elementary school – and those are built on skills learned in preschool and at home.

That means many of the problems that students face in high school find their roots in early math education.

https://news.osu.edu/how-to-improve-math-skills-among-american-children/