Most students have interacted with scientific representations that are used as teaching resources in schools. Often these external representations present challenges for understanding. By utilizing a framework based on an inferential, epistemic approach to scientific representations, we have analyzed students' representational constructions of the day/night process. This study identified the ways students build their representations or models based on their interpretations of school representations. The study participants were 151 students from a semi-urban primary school. Data were obtained through questionnaires and interviews. Analysis utilized the inferential approach to identify intentionality, interpretation, denotation, reasoning, and coordination rules in students' constructions. The results showed that only a few students were able to integrate school representations coherently as intended, and most of these students were in the upper grades. Even when students in the middle grades constructed reasoning processes, they did so use other elements of interpretation and denotation that are not equivalent to those in the school representations. We also found that most children failed to establish any discernible process that would indicate whether they used elements from the school model to infer explanations for the day/night process; that is, they had fragmented elements of representations that prevented them from making valid inferences. Finally, the approach described in this paper is useful for identifying difficulties that students face when dealing with scientific school representations since it offers elements for reconsidering the usual external representations that are used to teach science.