Why does Thurgood Marshall leave before the closing
arguments in the Joseph Spell case are completed?

African American students suffered damage from being treated differently.

Explanation:

Thurgood Marshall was a civil-rights attorney called by many "Mr. Civil Rights" for strongly advocating to end racism and promote equality in America. One of the greatest accomplishments of his career was winning the Brown v. Board of Education case (1954), in which he challenged the legality of American segregation. His argument to end segregation was that “separate but equal” facilities were indeed unequal and thus, a form of discrimination that instilled a sense of inferiority to African American students and undermined their self-esteem. Accordingly, it violated the 14th Amendment which guaranteed all citizens equal protection of the laws.