This study aims, in line with PISA ( Programmes for International Students' Achievement Evaluation) 2006, at constructing a structural equation model between variables considered to be associated with 15 year old Turkish students' science achievement scores and their responses to students questionnaire. In this sense, this is a relational research study. In data analysis, having identified the observed variables and the covered variables, the variables thought to predict science achievement and the relations holding between them were determined; and thus the extent to which the recommended pattern of relations was compatible with the real data was shown. On examining the structural equation modeling closely, it was found that the variable predicting students' science achievement best and the most significant factor determining achievement was "time". The other factors predictive of science achievement were found to be "the environment", "education" and "attitudes", respectively.