Question

What Precedent did the ruling in brown v. Board establish

Answer 1

Public schools could no longer be legally segregated.
 
 Brown v. Board of Education of Topeka, 347 U.S. 483 (1954), was a landmark decision of the United States Supreme Court that declared state laws establishing separate public schools for black and white students and denying black children equal educational opportunities unconstitutional. 
 I hope this helps. :)