While the last two decades have witnessed a growing body of research on the quality of student writing, research on the impact of the socio-cognitive approach on young learners’ writing has remained scarce. To fill this gap, this study investigates the effects of the socio-cognitive approach on the writing quality of 98 fourth graders in Singapore. The study addresses the question on whether there are any differences (in terms of macro-organization, complexity, productivity, and accuracy) in the compositions produced under the traditional methods and the socio-cognitive approach to writing program. Data sources include fourth graders’ pre- and post-test written documents over two years. Using the L2 Syntactic Complexity Analyzer, the written documents were analyzed in terms of macro-organization, fluency, lexical diversity, and complexity. Results showed that post-test writings of low-achieving students in the experimental group exhibited more development in story elements, use of different words, lengthier texts, and improvement in accuracy in terms of reduction of errors in capitalization, spelling, and punctuation. This study contributes to the field by suggesting the effectiveness of teaching writing to low proficiency learners through the use of a socio-cognitive approach.