May
17th
- 1954 – The United States Supreme Court hands down a decision for Brown v. Board of Education, overturning earlier rulings going back to Plessy v. Ferguson in 1896, and declaring that state laws that established separate public schools for black and white students denied black children equal educational opportunities.
18th
- 1927 – School board member Andrew Kehoe sets up a series of bombs in a Bath Township, Michigan elementary school, killing 45 people and injuring 58. The bombings were the deadliest act of mass murder in a school in U.S. history and became known as the Bath School disaster.
29th
- 1966 – A group of students at the Tsinghua University Middle School in China use the name Red Guards to sign two big-character posters issued on 29 May. The name would eventually become the label for students and other young people in the People's Republic of China, who were mobilized by Mao Zedong between 1966 and 1968, during the Cultural Revolution.