Lawyers for the plaintiffs relied on legal arguments, historical evidence, and psychological studies:
- In Plessy v. Ferguson, the Supreme Court had misinterpreted the equal protection clause of the Fourteenth Amendment. Equal protection of the laws did not allow for racial segregation.
- The Fourteenth Amendment allowed the government to prohibit any discriminatory state action based on race, including segregation in public schools.
- The Fourteenth Amendment did not specify whether the states would be allowed to establish segregated education.
- Psychological testing demonstrated the harmful effects of segregation on the minds of African American children.