The purpose of this research is to determine the scientific literacy levels of students in 9th, 10th, 11th and 12th grades of high school by using the scientific literacy research test. In the study, it was investigated whether there is a significant difference in scientific literacy among students studying at different levels in secondary education. Scientific literacy research scale developed by Carl J, Wenning was used to determine the scientific literacy levels of the students (Wenning, 2007). The research was carried out with a total of 187 students at different levels studying in secondary education. In the analysis of the data, arithmetic mean, standard deviation, t-test and analysis of variance were used to determine scientific literacy levels. According to the results of the research, there was a significant difference between the students' scientific literacy levels between the 9th and 11th grade students and the 12th grade students in favor of the 12th grade students, while there was no significant difference between the 10th and 12th grade students.