One look at the website of Seattle's Garfield High School (34% black/latino) CS Club website pretty much sums it up: http://www.garfieldcs.com/
The makeup is similar at the college level: sitting in on CS courses at UW you see a sea of white, east asian, and south asian faces. I can count the number of black or latino students (out of the several hundred enrolled students I saw) on two hands.
It's a pipeline problem, full stop.