Kids have more behavior problems and remember things poorly when they're hungry.
Kids that don't have a stable housing situation struggle to focus in school.
Kids with untreated medical problems struggle to focus in school.
Kids with absent parents (like a parent that tries to work multiple jobs) struggle in school
Kids with parents in unstable relationships (poverty screws up relationships and forces people into suboptimal relationships to combine resources) do poorly in school and are more susceptible to abuse
Kids that are the victim of abuse struggle to focus in school.