The inner city kids face challenges and hurdles, but you cannot say the families have no culture or support of education (unless you've never met one). But you also can't assume the suburban schools and families are models of good behavior either.
I believe most parents are doing the best they can most of the time. But suburban parents tend to have more resources to remediate and reteach and there's the real issue. A failing suburban kid will get tutoring. A suburban kid's parents can (usually) correct the math mistakes and grammar errors or teach the material again if the child fails. Inner city families tend to lack those resources that are needed to compensate for the lousy instruction their kids get in school.