The school board could have argued that the black teacher, who holds a master's degree, was marginally better qualified, or that it was acting to remedy past discrimination, but it didn't. Given the hostility on the Supreme Court to affirmative action programs that are not narrowly tailored to remedy overt past discrimination, the white teacher was almost certain to win her case. That would have set a major precedent which could have shot down affirmative action programs across the nation. It was a black-white thing.
Black doctorates are scarcer than hen's teeth, so they command a higher salary.
As for women doctorates in sociology, there are lots of them. When this case gets to the Supreme Court, we doubt the justices will allow the university to continue blatant race-based preferences merely because it desires to diversify the melanin mix on campus. That's not a good enough reason to junk the 14th Amendment and ignore the Civil Rights Act of 1964. Nevada's largest daily newspaper.