What you describe of black kids dying sounds nothing like “lack of expectations” to me. More like “forsaken communities”.
Not denying any longstanding cultural factors, people go into crime because of a combination of opportunity and motivation (from the studies I remember reading). “Lack of expectations” has never been measured as a problem as far as I know. And your sentiment just sounds like 21st century “white mans burden” all over again.
If poor crime policy is the problem then that’s another thing entirely. But then crime gets reduced by a combination of reducing inequality, increasing opportunities and yes good (sometimes draconian) policing. But you don’t mention that, only that black people in Chicago are criminal somehow because the political class has a “lack of expectations” for them.