Answer:
The event that helped to ease tensions between Japan and the United States over segregation in California's schools was the negotiation of the Gentlemen's Agreement.
Step-by-step explanation:
The Gentlemen's Agreement was an informal agreement between Japan and the United States of America reached on February 15, 1907 in order to reduce Japanese emigration to the US and avert racial segregation of the Japanese-Americans in America.
The agreement, which also aimed to ease tensions between the two superpowers of the Pacific, was never ratified by the Congress and ended with the entry into force of the 1924 Immigration Act.