The Brown vs. Board of Education was controversial for several reasons, including:
1) Overturned the Supreme Court case ruling in Plessy vs. Ferguson- The Plessy vs. Ferguson (1896) case established the idea of "separate but equal" facilities for blacks and whites in American society. This course ended this precedent in America.
2) It ruled segregation in public schools illegal- This ruling would eventually end segregated schools, which have existed since the beginning of the 20th century.