This is obscenely long. Read the short version if you don’t have much time. Read the rest if you like.
The Short Version: There is a lot of complicated math in the world. We tend to venerate that math for its complexity, and not tell our students about it because they’re not ready to understand it yet. This is terrible. One of the worst things we can ever tell our students is, “You haven’t learned ____ yet, so you can’t learn ____.” We throw up our hands in frustration when our middle schoolers don’t know multiplication facts. “How will we ever teach linear functions?”, we cry.
I am totally guilty of this. It takes a leap of faith to trust that a student struggling with division can work with rational numbers. Assuming they can’t means math is sequential. I don’t think it’s that cut and dry. Sure, prime factorization helps me factor polynomials, but what if you happened to start with factoring polynomials. Is that impossible?
Sending the message that the second step is unattainable until you’ve reached the first is a problem for two reasons: