My experience as well—I went to a Montessori school up through Kindergarten. I absorbed enough that I could coast without learning any new math until 3rd grade, when we started doing long division. My teacher either didn't notice or couldn't help when I started suddenly struggling. It put me off math for the rest of school.

It's still a sore point for me 30 years later. I do a lot of graphics programming, and I know I have the type of mind that can handle complex math, but I missed that fork in the road.