The study reported here examined the relationship between classroom culture and Korean high school students informal reasoning abilities. Classroom culture was represented by four factors: epistemological beliefs, argumentativeness, verbal aggressiveness, and classroom climate. The study addressed the following research questions: (1) How do students epistemological beliefs, perceptions of classroom climate, argumentativeness, and verbal aggressiveness differ between different types of schools? (2) How do students reasoning skills differ between different types of schools? (3) How do the four variables of classroom culture correlate? (4) How do students epistemological beliefs, perceptions of classroom climate, argumentativeness, and verbal aggressiveness correlate with their argumentation skills? (5) What are the best predictors of students argumentation skills? Participants of the present study were selected from three different types of college preparatory schools located in urban areas of Korea: Foreign Language High School, Science High School, and regular type public school. The data analysis of the present study indicated that students with more sophisticated epistemologies produced more premises and arguments and the quality of their arguments tended to be higher than students with less sophisticated epistemologies. Further, argumentativeness correlated positively with the number of arguments produced and the quality of arguments, while verbal aggressiveness correlated negatively with students informal reasoning skills. The data analysis also indicated that students who had more sophisticated epistemologies were more argumentative and less verbally aggressive, and they felt freer to express their opinions about social issues in their classrooms. Students of the three schools differed in their argumentativeness and classroom climate. Foreign Language High School students were more argumentative and felt freer to express their opinions about social issues than students of the other two schools. School type also correlated with students informal reasoning skills. A multiple regression analysis indicated that the school type was the best predictor of students performance in argumentation. Foreign Language High School students performed better than the other two schools students in most aspects of argumentation skills. Science High School students stated more premises and arguments than the regular public school students.
