Studies of early writing recognize that learning to write is a complex process requiring students to attend to the composition of the text and the transcription of the ideas. The research discussed here examined six dimensions of early writing--text structure, sentence structure, vocabulary, spelling, punctuation, and handwriting--and how each dimension relates to message construction. Specifically, this research aimed to consider the relationships between the authorial and secretarial aspects of writing, in order to support formative assessment and teaching. The research also considered whether there were underlying clusters of students who were engaging with the various dimensions in differing ways as they learned to craft texts. The analysis of data showed a clear conceptualization of the authorial and secretarial aspects of writing, as reflected in a tool for analysing writing. The three authorial dimensions and three secretarial dimensions of writing were well defined statistically. Three clusters of students were identified as having varying degrees of competence across the six dimensions of writing: a group with consistently low scores; a group with consistently medium scores; and a consistently high-scoring group. Attainment for SES groups was reflected in the writing dimensions, and gender differences were also evident; however, the variance explained by gender and SES was small to moderate. The study has implications for supporting students who are at present struggling with the challenges of early writing. The results suggest that when teachers address the dimensions of the writing process in combination, based on an informed analysis of students' needs, they can focus their teaching and select instructional approaches to increase the efficacy of their teaching.