"Intimate Apparel"  By Lynn Nottage.

Go for the musical "Purlie" - one of the greatest musicals of the 20th century.

On a smaller scale - the play "Permanent Collection" explores the harm done to both sides when racism rears its ugly head, that it's not just whites who are capable of being racist.

          A good one to do would be "Juba". It is about the dance Juba who is credited with inventing Tap dancing. It show how even during the era of the minstrel shows Juba, a black man, was able to stay at ritzy hotels, have a private carriage and awesome respect. It is a great positive show of one man rising above it all.
          It is also great for teaching all involved about some of the better minstrel show producers. Some of who used their productions to get African music, culture, and hardships to the public.
          Bit of trivia. Did you know the producer who introduced 'Dixie" to the world, wrote it for a scene where a freed slave was dieing on the streets of New York? He had the man sing Dixie as he was dieing. Basically telling the audience he would rather have been dieing a slave down south than a "Freed Man" in the north, where he was still treated as less than an animal. This producer was also one of the first ones to put Africans on stage in make up. He also spent time on the plantations living with the slaves and in Africa paying them for music and dance choreography. After the South took "Dixie" for their anthem he was prohibited from performing in the North. So he moved to Europe.