As a kid, I 100% noticed race. I doubt most did. My elementary school is around 25% black kids, 50% hispanic, 10% asian, and 25% white. I think it was just as bad when I went to it.
Reading and math were organized by intelligence. Those classes had only white and asians. Not even a single black or hispanic. Other than those 2 classes, the rest of the classes were integrated as fuck.
A few months ago, I found my old diary from elementary school. I was reading a few pages and saw the page where I wrote that I didn't want black kids in any of my classes as 1 of my 3 wishes. It was not my fault. I suffered so much as a short nerd. I noticed how it was pretty much always black and few hispanic boys causing problems in class. Without them, my math and reading classes were so peaceful.
Going to a diverse public school teaches why race is so important.