Your science teacher is an ignorant bigot who should not be teaching people. Good Lord. We are all the same, human beings, and there really is no such thing as “race”, just difference in morphology, as @dpworkin said. Your teacher needs to get back in his/her time machine and head back to the deep South prior to the 1960’s.
Actually, I would like to know if you go to a public school and if so, what is the name and location? I have a few choice words for your principal regarding this science teacher.
edit… ugh, I am seriously disgusted by this. If that science teacher knew anything about genetics, they would know that diversifying the genetic line is actually quite beneficial to a species. erg.