The use of student ratings to measure instructors' teaching performance and effectiveness in tertiary education has been an important but controversial tool in the improvement of teaching quality during the past few decades. This is an attempt to explore non-instructional factors of student evaluations by discussing and reviewing relevant literature with regard to the most common non-instructional factors in student ratings. Moreover, semi-structured interviews were used with 14 college instructors. The findings show that most of the teachers support the use of student evaluations as a means of quality control and teaching improvement. However, the great majority of teachers expressed their concerns about the non-instructional factors which affect student ratings and make them meaningless. They reported that gender, time of evaluation, expected grades, nationality of the instructor, and other factors can affect student ratings. The study proposes some recommendations which might make student evaluation practices more useful and informative.