teaching about race

Today when I was teaching about America to the seventh graders, I tried to teach them that people come from different countries but all live in America and speek english. To my suprise most understood and one girl even asked about descrimination. I was very suprised and not sure how to answer, but I had to tell the truth so I told her that there was descrimination. The students asked a little to many questions. This is fine I do not mind.