The uses of portfolios, reports, and records in assessing children in early childhood education are well-known. However, other possibilities have emerged related to the use of assessment rubrics as instruments for evaluating children and enhancing the quality of reports. In this study, we investigate the knowledge of early childhood education professionals regarding assessment rubrics, addressing the challenges and contributions associated with the construction of a collective instrument model. We used the case study approach as a methodological element. The data revealed a superficial and limited understanding of the topic. Generally, participants were unfamiliar with the instrument, mistakenly associating it with a checklist. Simultaneously, they expressed varied interpretations, indicating a weak knowledge base. The collaborative construction of the instrument highlighted substantial challenges, with the main one related to defining quality criteria. Additionally, some contributions were identified, such as the opportunity for socialization and knowledge exchange, a process translated as formative for the participants. The findings of this study can be applied in teacher training courses within the context of universities and education departments.