Final answer:
Kenneth and Mamie Clark's social science research, particularly the 'doll test', and the Supreme Court's unanimous ruling against 'separate but equal' doctrine in public education had the most impactful influence following the Brown v. Board of Education case.
Step-by-step explanation:
The experts from the Brown v. Board of Education decision that had the strongest impact on public education and national policies were the social scientists, Kenneth and Mamie Clark. Their study, the 'doll test', significantly influenced the Supreme Court's decision by demonstrating psychological effects of segregation on African American children, leading the court to declare in the landmark decision that 'separate educational facilities are inherently unequal'. This ruling initiated the legal dismantling of segregation in public schools, challenging the precedent set by the Plessy v. Ferguson decision and catalyzing the civil rights movement.
Another crucial aspect of Brown v. Board of Education was the establishment of the concept that separate but equal was not just unfeasible, but it also produced a sense of inferiority among Black students that could only be remedied by ending segregation. This was coupled with the Supreme Court's unanimous ruling that de jure segregation was unconstitutional, setting a precedent for civil rights advancements and posing a direct challenge to Jim Crow laws. The subsequent decisions and actions, including the 'all deliberate speed' mandate in Brown II, and defiance through the 'Southern Manifesto', highlighted the complexity of desegregation efforts, impacting both public and private school policies and emphasizing the Federal Government's role in enforcing educational equality.