Flexible grouping is a method of class management that use various types of activities to design a teaching-learning process. The groups can be changed according to the needs. With various approaches, students engagement and progress are going to increase. To prove this, research was conducted in a private school. Grade 9 students who chose Biology and/or Global Perspectives classes were included in the research. Data were collected qualitatively by class observation and interviews. Both students and teachers were interviewed about their opinions and feelings toward the flexible grouping method. Results showed that students engagement increased. Teachers also considered using this method as a regular activity in the class.