4. which effect can be traced directly to the supreme court’s ruling in the plessy vs. ferguson?

This is all I know, because I'm in 8th, sorry. The Supreme Court Case Plessy vs. Ferguson (163 U.S 537), ruled and upholded every state's laws against racial segregation in public facilities, you know, coffee shops, banks, etc. Please note that Brown vs. Board of Education, 1954, was the one that ruled unanimous that racial segregation should be banned in public and private schools. Remember the Jim Crow laws. Hope this helped.