The purpose of the current study is to determine to what extent the following four variables explain K-8 students’ SBS  success  levels;  these  variables  being  attendance  to  private  SBS  preperation  courses,  multidimensional  perfectionism, parental attitude types, and test anxiety. SBS is a nationwide, high stake, high school placement test  taken  by  middle  school  students  in  the  Turkish  education  system  since  the  2007-2008  school  year.  The  sample  of  this  study  consists  of  460  cluster  sampled  8th  grade  students,  of  which  257  are  girls  and  203  are  boys  all  from  the  city  center  of  the  province  of  Tokat,  Turkey.  The  Multi-dimensional  Perfectionism  Scale  (MPS),  Parental  Attitude  Type  Scale,  Westside  Test  Anxiety  Scale,  and  a  personal  information  sheet  were  used  to  collect  data  which  was  then  analyzed  using  hierarchical  linear  regression,  independent  group  t  tests  and chi square tests. According to the findings, the most effective variable in determining a student’s level of success is attendance to private preperation courses. Other significant predictors of success on the SBS are the espousal of a perfectionist attitude by parents and a student’s level of test anxiety. Moreover, the most effective factor influencing SBS scores of students who do not attend preperation courses is his parents’ adoption of an authoritarian attitude. While the “Order” dimension of the MPS and “test anxiety” were negative predictors of students’ success on the SBS, “responsibility-centered parents’ attitude” was positively related to the students’ scores. “Doubt from behaviors” was the most effective negative predictor explaining the SBS scores of students who did not attend private SBS preperation courses. The findings of the study suggest that as one’s income level increases, so does the duration of time spent attending SBS prep courses, and this increased level of success can also be attributed to effective parent involvement in students’ lives. However, family’s income stands as a definite medium, explaining students’ SBS success. As a result of the current study, SBS preperation courses has  been  found  to  be  the  most  defining  factor  in  students’  SBS  scores.  According  to  the  findings,  student’s  success on large scale tests are mainly affected by extracurricular activities, such as courses or private lessons. Key WordsParental Attitude Type, Private SBS Courses, Perfectionism, SBS, Test Anxiety.