In the past couple of decades there has been an increased interest in how content is construed, communicated, evaluated and renovated within different disciplines such as science, history or literature. Research on discipline specific reading and writing has shown that students need to be explicitly taught these specialized ways to read and write within the context of a certain discipline in order to grasp the differences. However, there are few studies focusing on how such abilities are visibly emerging in early school years and even fewer on what specifically characterizes subject specific reasoning in early school writing. The purpose of the presented research is therefore to propose a text analytical method informing an in-depth understanding of subject specific reasoning in early school writing. To this end, the paper provides a suggestion, based on text analytical tools inspired by Systemic Functional Linguistics, of how to examine how children make use of linguistic resources for reasoning in early literary and scientific texts. Drawing on results from previous conducted studies, the presentation will expand on how reasoning in literary texts in primary school can mean both to explore a diverse world in text, as well as more uniform ones, while reasoning within scientific texts, seemingly homogenous, are construed through the use of a variety of linguistic resources. The results thus makes evident that there’s a diversity of linguistic resources in use, pointing to the potentiality for development of broader writing repertoires of children in early school years. Finally, the results point to the need for research regarding the nascency of other subject specific reasoning, as well as how, and what aspects of text written in early school years are valued by assessing teachers.