The correct answer is the ruling declared that school segregation was unconstitutional.
Before the Brown vs. Board of Education case, segregated schools for black and white citizens were allowed thanks to the ruling in the Plessy vs. Ferguson Supreme Court case. In this case, the Supreme Court ruled that "separate but equal" was constitutional.
However, the Brown vs. Board of Education overruled this case. The Supreme Court justices ruled in favor of the Brown family and their claim that segregated schools for black and white citizens clearly violated the 14th amendment of the US Constitution. More specifically, it violated the Equal protection clause.