This study is designed to explore organizational socialization and organizational performance levels of secondary school teachers and the relation between the two variables mentioned. The study is designed as correlational research. The target population of the research consists of 5744 teachers who work in public and private Anatolian high schools in the center of Ankara, the capital city of Turkey. Using the stratified sampling technique, 650 participant teachers have been included in the sample. This study has revealed that the participants are relatively more socialized in the organizational socialization language factor, which is followed by socialization levels in the following factors: performance proficiency, people, history, organizational goals and values, and politics. The socialization levels of teachers indicate significant differences in the history and language factors according to gender. In all the factors, the participant private school teachers are found to be more socialized than the public school teachers. Their organizational performance levels significantly vary according to gender and type of school. The performance of teachers in private schools is relatively higher than that of those in public schools. There is a significant, moderate positive relation between organizational socialization and organizational performance.