Experiences of competence and autonomy are essential for intrinsic motivation, social development, and well-being. However, little is known about how these constructs are related to previous achievement in mathematics. In the present study, we investigated whether ninth-graders (N = 83) with different levels of achievement differ in their experiences of competence and autonomy and whether their experiences change during a teaching intervention focused on modelling. We found that high- and low-achieving learners did not differ in competence or autonomy. However, competence and autonomy developed differently across the time period of the teaching intervention. The experience of competence increased for high achievers, and autonomy decreased for low achievers. The results contribute to a better understanding of how intra- and interindividual differences are related to competence and autonomy and provide insights for effective interventions.