In this case, the Supreme Court ruled that segregated schools were unconstitutional.
Up until this point (1954) segregated schools had been legal. The idea (laid out in Plessy v. Ferguson in 1896) was that racial segregation did not violate the 14th Amendment's guarantee of equal protection of the law so long as white and black schools were equal to one another. This was the doctrine of "separate but equal." In Brown, the Court overturned this interpretation. It said that schools that were racially segregated as a matter of government policy could never be equal. Therefore, schools could no longer be segregated on the basis of race.
Warren Court ruled that "separate but equal" was unconstitutional and that it is a denial of equal protection of the laws under the 14th Amendment.
Written by Chief Justice Earl Warren, the opinion declared racial segregation illegal in public schools.