Our country's having underachieved repeatedly in the international examinations such as PISA, TIMSS etc., has made us consider that there are some problems related to our education system. The lowness of achievement levels might be affected by many factors such as the student, the program, and the teacher being in the first place. Of these factors, it is the teacher who is of great importance both because of being the person implementing this program and being the factor on the performance of whom measures can be taken easily. Starting from this point on, in the present study, the opinions of teachers about the lowness of students' achievement levels on these exams were examined. To achieve depth in the investigation, first the questions having addressed to students in PISA implementations were asked to the teachers in written form and answers were received and then they were asked for their opinions. The study revealed that the teachers regarded the insufficiency of the contents of the program and that of the teachers' accumulation of knowledge as the main reasons for students' low achievement levels. It has been concluded that working on these two factors and including such kinds of questions within the exams carried out nationally are necessary to increase students' achievement levels.