Tutorials are an essential part of the academic teaching process. They play an important role in students' understanding of the material and have a direct influence on their final marks. Selection of proper tutoring policy for improving students' success in engineering disciplines is a subject investigated all over the world. It is common to think that efficiency of tutorials in smaller groups is higher. However financial considerations limit sub-division of classes into small groups. This paper is focused on the issue of the preferred teacher of these sessions – lecturer (faculty member) or teaching assistant. The current study examines the effect of this administrative decision on students’ performance, as measured by ratings of their teachers, and also by students' final grades. The influence of additional factors like class size, students’ grades, or majors is also examined. Our findings show that there is no significant advantage of tutorials taught by teaching assistants in small groups over those taught by lecturers in plenum.