I agree with the multiple methods, but I believe that certain things in math are considered to be basic building blocks (such as single digits add/sub/mul/div) that should be memorized similar to in sports how certain movements are considered basic and are practiced until it becomes muscle memory.

As for the difference in outcome of white vs non-white in poor neighborhoods, I feel there are more at play than institutionalized racism, but it is incredibly difficult to have a nuance discussion on the topic.