The acoustic environments of classrooms often fail to comply with existing norms or recommendations. Noisy environments can not only affect children's listening abilities but also lead to a decline in cognitive performance. This study presents preliminary results on how background noise can influence primary school children's cognitive and learning processes. The CoEN (Cognitive Effort in Noise) app was developed and used to assess children's cognitive effort using standardized neuropsychological tests. Children attending two primary schools were tested in their classroom environment under two acoustic conditions: quiet and noisy. Performance was also correlated with acoustic environmental measures and a self-report questionnaire on perceived cognitive effort. The preliminary findings only partially support the hypothesis that noise negatively impacts cognitive performance. Noise was found to negatively affect children's performance on attention tasks in the first school, while in the second school, children performed better in noise on both attention and inhibition tasks, as well as a writing task. Unlike the first school, the second school had a reverberation time that did not meet regulatory standards. These initial findings suggest interesting hypotheses and directions for future research. At the same time, they reveal some weaknesses in the experimental protocol that need to be addressed to further investigate the emerging hypotheses.