Brown v. Board of Education was a major reversal of US racial policies. Prior to the ruling, public accommodations had been based on the 1896 ruling in Plessy v. Ferguson. Plessy v Ferguson held that public accommodations could be "separate but equal." In Southern States this was taken to mean that Students could be placed in either "black" or "white" schools based on their race, so long as the schools maintained the appearance of being equal.
However, public accommodations for racial minorities in the South were anything but equal. "Black" schools were typically allocated less money than comparable "White" schools. When the dollars were equal, the "Black" school was typically bigger, with a larger student body, and consequently more expenses than the "White" school. And this was evident in other public accommodations as well.
Brown v. Board of Education held, "Separate is inherently unequal." This completely replaced the Plessy v. Ferguson standard. According to the terms of the ruling all public schools had to allow students to attend regardless of race. Although the ruling did not necessarily apply to private schools, most private schools also adopted the rule.
Brown v. Board was also "ahead of its time." Brown v. Board was in 1954, ten years before most "desegregation" campaigns began (e.g. the Montgomery Bus Boycott, Freedom Riders, March on Washington etc.) Brown v. Board was the catalyst that emboldened supporters of civil rights, and paved the way for broader desegregation in all public accommodations and services.