Read the excerpt from the Supreme Court’s Brown v. Board of Education decision.
We conclude that, in the field of public education, the doctrine of "separate but equal” has no place. Separate educational facilities are inherently unequal. . . .
[The courts must issue] orders and decrees . . . to admit to public schools on a racially nondiscriminatory basis with all deliberate speed the parties to these cases.
Brown v. Board of Education,
Chief Justice Earl Warren,
1954–1955

According to the Supreme Court, why was the doctrine of "separate but equal” no longer acceptable?

Segregated schools had become unusual after recent court orders.

Schools already admitted African American students whose skills were equal to those of white students.

Separate schools for African American students were almost always unequal to white schools.

Public schools almost always tried to be racially nondiscriminatory.