This paper deals with the effect of student characteristics from a case study on the different teaching evaluation scores under the same conditions of professor and course characteristics. In particular, focusing the evaluation score gabs caused by different course achievements of two classes, we can analyze the influence of the student characteristics and interpret the meaning. This case study shows that the student characteristics can lead out a distinct difference in the teaching evaluation scores under the most factors related to professors and courses are controlled, In conclusion, this case study could be appropriately used to support the interpretation of the student characteristic hypothesis among several hypotheses about the meaning of correlations between student achievement and teaching evaluation.