Final answer:
The Supreme Court ruled in the case Brown v. Board of Education that segregation in public schools was unconstitutional, overturning the precedent set by Plessy v. Ferguson. The ruling was based on the violation of the equal protection clause of the Fourteenth Amendment.
Step-by-step explanation:
In the landmark case Brown v. Board of Education, the Supreme Court ruled that segregation in public schools was unconstitutional. The court unanimously decided that the practice of separating students based on race violated the equal protection clause of the Fourteenth Amendment. The ruling overturned the previous precedent established by Plessy v. Ferguson, which had allowed segregation under the concept of "separate but equal."