When two bodies collide, the body with the larger mass exerts the greater force is a widely known but still common misconception. This study aims to compare the effectiveness of a conceptual change text and a traditional expository text to overcome this target misconception. Then to reveal the effect of students' readiness on this situation. For this, a case study was conducted with 92 students (ninth grade) from two different types of schools. One of these schools accepts students by a nationwide central placement exam, and the other does not need the exam. The students in the second type of school are generally very low in academic achievement. A focus group consists of 24 students examined in detail. The students in the focus group selected with a maximum variety of sampling based on the achievement. Multiple-choice questions in different contexts and simulation-assisted-interviews were used for data collection. It is seen that the type of text did not cause any difference in the school that students with high academic achievement. Conversely, a difference was found in favor of the conceptual change text in the second school. The results of the research point to the fact that the conceptual change text was more effective than the traditional expository text in the student group low in academic achievement.