This study aims to identify the factors that explain the quantitative development of students’ writing performance. The participants included forty-eight preservice Arabic teachers who were expected to graduate from the College of Education at Kuwait University during the fall 2022 semester. The methodology employed is a mixed-methods sequential explanatory design, which involves a quantitative phase followed by a qualitative phase. During the quantitative phase, the participants took part in a twelve-week writing workshop, during which their written performance was examined four times. The results revealed a statistically significant improvement in their written performance at the end of the program. During the qualitative phase, the interviews revealed that the key factors accounting for their improved performance included reading prior to writing, adopting prewriting practices, such as discussion, concept mapping, and inner speech, developing a stress-free first draft, engaging in significant revision, allowing for a multiday editing process, and leveraging the benefits of peer-review. This study emphasizes the significance of teaching the writing process to language-arts teachers in literacy classes in teacher preparation programs, as well as the need for offering professional development opportunities for in-service teachers. Moreover, the findings highlight the need for conducting future research.