This case study investigated moments of agency and constraint experienced by Catherine, an elementary teacher in a superdiverse classroom ecology in Southern France as she implemented the French National Cycle of instruction for the elementary grades. The findings revealed that a variety of factors constrained her ability to enact effective instruction, including class size, the curriculum, and her training and professional development. Despite the challenges that she faced, the moments of agency that Catherine experienced were constructed by her in collaboration with her students as agency through bricolage. The study highlights the critical need for teacher education and professional development in France to integrate principles and practices for preparing all teachers to enact cultural and linguistically responsive pedagogies.