The subjects of the study consisted of 60 ninth grade high school students [33 boys (55%) and 27 girls
(45%)] with a mean age of 14.5 years in two classes selected from a high school in an urban area in Nigde,
Turkey. The classes were selected randomly (Fraenkel and Wallen, 1996) from the school. One group (9-B class)
was randomly assigned to the experimental group (η= 30), while the other (9-C class) formed the control group
(η=30) of the study. All the students in the groups took the Level Defining Examination, known as SBS (Seviye
Belirleme Sınavı) in the previous year in order to enter in this high school. The academic achievement levels of
these students were understood to be similar in relation with their SBS scores in the previous year. Meanwhile,
the SBS scores of the students were taken from the school administration.