The present investigation examined the development of Taiwanese senior high school students’ narrative and argumentative writing. The 212 participants were all male students from a senior high school in southern Taiwan, and a mixed-method approach was adopted to conduct two studies.

Study 1 was cross-sectional and quantitative, with 100 Year 1 and 100 Year 3 students as the participants. The participants’ written texts were scored and analyzed holistically and in terms of syntax, vocabulary, accuracy, and fluency. The results indicate that Year 3 participants received higher holistic scores and used syntactic structures that previous research (e.g., Schmid et al., 2011) has considered to be more complex, including more complex sentences, relative clauses, and non-finite clauses, as well as longer sentence length. Year 3 participants’ writing also had greater lexical sophistication, diversity, and density than that of Year 1 participants. There is, therefore, evidence of writing development. The groups differed in the types of errors that they produced most commonly, but there was no significant difference in writing fluency.

Differences across genres were also observed. Year 1 students received higher scores for their narrative writing, as opposed to argumentative, but Year 3 students had similar scores for the two genres. A questionnaire survey suggests that Year 1 students were more interested in narrative writing, which might explain their better performance in that genre (Yoon, 2017a). Genre also influenced the textual linguistic features. The study partially supports the findings of previous studies (e.g., Beers & Nagy, 2009; Lu, 2011) that argumentative writing results in more linguistically complex structures—that is, longer sentence length, complex sentences, nonfinite clauses, and less common words. However, the lexical and clausal analysis showed greater lexical diversity and greater use of relative clauses in narrative writing. This genre difference might arise in part from the different communicative purposes of the two genres, while the writing prompts used might have also played a role. The accuracy analysis showed different error types across genres, but no differences were found in fluency.

Study 2 focused on the longitudinal L2 writing development of another set of participants: 12 Year 1 Taiwanese senior high school students. The observation period was approximately two years. The participants’ development was found to be non-linear in the holistic scores that their texts received, the use of linguistic features indicating development, and the use of learning strategies and practices. The text-composing strategy analysis showed more similarities than differences across time and genres. Local planning, translating, mechanical refining, and rhetorical refining were the four most frequently used strategies. In writing both genres, the participants experienced the same problems, including limited English proficiency, insufficient life experience, and difficulty with the text organization and content generation. They also encountered problems specific to each genre: describing an interesting story in narrative writing and dealing with the counterargument and convincing the audience in argumentative writing. Learning strategies and practices—such as attending cram schools, committing to self-directed writing practice, using extramural approaches to learning English, imitating expressions of quality works, and benefiting from the school teacher—were common among the participants. Furthermore, the role of the exam-oriented educational setting influenced the participants’ strategy use to some extent.

In conclusion, the study contributes to the general understanding of the “evolving L2 writing capacities” of EFL senior high school students (Manchón, 2012, p. 3) and how the students’ writing skills developed in different genres. The study observed that L2 writing development is a “dynamic process” (Lowie & Verspoor, 2007, p. 7). Theoretical, methodological, and pedagogical implications are drawn, and limitations of the present study and recommendations for future research are also reported.