The historical legal ruling regarding public education that declared segregation unconstitutional was Brown v. Board of Education (1954). This landmark Supreme Court decision overturned the "separate but equal" doctrine established by Plessy v. Ferguson (1896), ruling that racial segregation in public schools violated the Equal Protection Clause of the 14th Amendment. The court found that segregated educational facilities were inherently unequal and detrimental to African American children, essentially setting a precedent for desegregation across various public sectors. The decision marked a significant advancement in the Civil Rights Movement, galvanizing activism and initiating reforms to address institutional racism in America.