Many years ago，an experiment in education was carried out in secret at a school in England.The school had two classes for children of the same age.At the end of the school year an examination was held，in order to select the children for the classes of next year.However，the results of the exam were never made known.In secret，based on their performance in the exam，the higher－performing and lower－performing children were divided equally between the two classes.Only the headmaster and the psychologists knew the truth.Teachers for the next year were carefully selected for equal ability and experience.Even the classrooms were chosen with similar facilities (设备)．Everything was made as equal as possible，except for one thing：one was called “Class A”，the other，“Class B”．
