A curriculum is supposed to be something that the teachers and authorities would construct. Recently, more studies have focused on student contributions to curriculum development. These studies largely framed listening to student voices in the planning processes. However, actual voices can be heard in the process of running classes, and such needs also help the teachers realign, redesign, and redevelop curricula improvisationally. This is also a ‘co-curriculum’ by listening to the voices of students who stumble. This essay aims to conceptually discuss the possibility of recognising students’ stumbles during the classes as seeds for improvisational curriculum development and design, positioning the students as curriculum co-makers with their teachers. Such attempts require a climate where the right of every student to learn is recognised and valued, and it depends on school leadership and management to highlight the importance that the learning opportunities are provided to every student.