Ask HN: On Math Proficiency for Elementary School Kids

My son's elementary school doesn't seem to focus much on math (despite being a highly rated school). I've discovered that many parents send their children to after-school math programs to get this education. That creates a system where you play the game, or fall behind (which in math, I imagine, is a gravity well).

It's hard to know what's expected at each grade level, and where diminishing returns are in terms of learning, as well.

How, then, should we evaluate extracurricular resources?

For example: after school programs (like, Russian School of Math). They're expensive, and often require an annual commitment. But is there evidence they produce "successful" outcomes (how is that even measured). Are they snake-oil? Etc.