Prejudice is learned young. If you want to influence kids, you don't do it with mayors or presidents making press statements. You do it through visual messaging on TV.
The Palestinians know this. That's why they target their kids with cartoons bashing Jews. Hilter knew it; he had his Nazi Youth Corps. North Korea has twisted caricatures of Americans posted in their schools. Racists know how to keep their ideology going.
Why not get the advertising industry involved? An ad featuring a poor black kid being excluded by white kids playing a basketball game in the playground would have much more impact on someone that age than a speech from adults.
Remember those '70s ads of the crying Indian standing by some trash washed up on the river shore? That anti-litter campaign had a real impact at the time. That's what reaches people.