What was the main reason why it was more expensive to operate a school system in the south than in the north?

Because the policy of segregation practiced in the south.

Red cells contain a special protein called hemoglobin, which helps carry oxygen from the lungs to the rest of the body and then returns carbon dioxide from the body to the lungs so it can be exhaled. Blood appears red because of the large number of red blood cells, which get their color from the hemoglobin.