Recent instructional reforms in science education aim to change the way students engage in learning in the discipline, as they describe that students are to engage with disciplinary core ideas, crosscutting concepts, and the practices of science to make sense of phenomena (NRC, 2012). For such sensemaking to become a reality, there is a need to understand the ways in which students' thinking can be maintained throughout the trajectory of science lessons. Past research in this area tends to foreground either the curriculum or teachers' practices. We propose a more comprehensive view of science instruction, one that requires attention to teachers' practice, the instructional task, and students' engagement. In this study, by examining the implementation of the same lesson across three different classrooms, our analysis of classroom videos and artifacts of students' work revealed how the interaction of teachers' practices, students' intellectual engagement, and a cognitively demanding task together support rigorous instruction. Our analyses shed light on their interaction that shapes opportunities for students' thinking and sensemaking throughout the trajectory of a science lesson. The findings provide implications for ways to promote rigorous opportunities for students' learning in science classrooms.