Segregation violates the “equal protection clause” of the 14th Amendment
In 1896, the Plessy V. Ferguson decision was decided by the Supreme Court where they ruled that segregation was constitutional as long as the facilities for black and white people were the same. This led to the Jim Crow Laws being formed in Southern United States which were placed to enforce segregation and marginalize black people.
The Supreme Court's decision in the Plessy V. Ferguson case as well as the Jim Crow laws resulted in the segregation of schools. Even though black and white people were supposed to be "separate but equal" white people were always given the facilities that were in better condition.
After Oliver Brown's daughter was denied entry to an all white school in Topeka Kansas, he filed a lawsuit against Topeka Kansas's Board of Education. In his lawsuit he claimed that white schools and black schools were not equal which goes against the separate but equal doctrine.