Being part of the German didactic tradition, reflective thinking was first coined by Wilhelm von Humboldt two-century ago. Reflective thinking helps individuals to develop strategies in order to overcome the problems that they encounter. Investigating the reflective thinking skills of students for problem solving is important to identify students that may need extra assistance to develop their reflective thinking skills. In this study, the reflective thinking skill level of secondary school students is investigated. The cross sectional survey design is used in this study. The data were collected from 297 middle school students who are in 6th, 7th and 8th grades in Zonguldak city center of Turkey. The scale measuring the reflective thinking skill towards problem solving was used for the data collection. The descriptive statistic, the one-way ANOVA and the Bivariate correlation were used for data analysis. Findings revealed that secondary school students' reflective thinking skill levels are above the average. However at the same time participating students' course grades for the math course and for the science and technology course were close to the maximum score. This shows that academically successful students' reflective thinking skill level tend to be high. Another significant finding of this study is that female students' reflective thinking skills are higher than male students'reflective thinking skills. The third finding of the study revealed that there is no correlation between the math course grades and the reflective thinking skills of the secondary school students. Similarly no correlation was found between the science and technology course grades and the reflective thinking skills of the secondary school students. However a statically significant relationship is found between the questioning skill level of the students and their course grades in the science and technology course. It is suggested that reflective thinking skill level should not be used as a predictor of the course grades for investigated courses for the study population. More research studies are needed to make generalizable conclusions about the relationship between the reflective thinking skills of the elementary school students and their academic achievement. The results of the study reveal that the reflective thinking skill of secondary school students are above the average but there is a room for improvement. It is also found that female students' reflective thinking skills are higher than the male students'. Moreover a statically significant relationship is found between the questioning skill level of the students and their course grades in the science and technology course. It is suggested that reflective thinking skill level should not be used as a predictor of the course grades for investigated courses.