Given the following passage  "The process of desegregation at Washington University began in 1947 with the School of Medicine and the School of Social Work. During the mid and late 1940s, the University was the target of critical editorials in the local African American press, letter-writing campaigns by churches and the local Urban League, and legal briefs by the NAACP intended to strip its tax-exempt status. In spring 1949, a Washington University student group, the Student Committee for the Admission of Negroes (SCAN), began campaigning for full racial integration. In May 1952, the Board of Trustees passed a resolution desegregating the school's undergraduate divisions.",  answer the following question. Note that the answer is present within the text.  Question: What aspect of Washington University did the pressure groups' campaign threaten?
Answer:
its tax-exempt status