What was the decision that declared segregation in schools unconstitutional?

Brown v. The Board of Education.

Explanation:

Brown vs the Board of Education was a court case that dealt with segregation. It overturned the previous case in 1896, Plessy v. Fergusson.

Homer Plessy was an African American who was arrested for sitting in a whites only area. The case was appealed to the Supreme Court and Plessy lost the case with a vote of 7-1. They stated that it was separate but equal.

It wasn't until 1954, 50 years later until it was changed. It was with the Brown family with Thurgood Marshall as their lawyer. They challenged the Plessy v. Ferguson case. And it resulted with the Supreme Court agreeing with Brown unanimously. Declaring that segregation in school unconstitutional.