Does Higher Grade Indicate More Complex Language Usage? Exploring Syntactic Complexity Development Among High School EFL Learners

This article aims to investigate the longitudinal Syntactic Complexity (SC) development of English as a Foreign Language (EFL) learners and the variations by grade level. This study conducts a longitudinal analysis of SC development among 199 high school EFL learners in eastern China. The corpus contains 920 argumentative essays on scientifically and socially contentious topics. We employ the Second Language Syntactic Complexity Analyzer (L2SCA) to examine syntactic features in these essays through 11 computerized indices measuring different dimensions of SC (i.e., coordination, subordination, phrasal complexity). Multi-level regression analyses are used to depict SC development and cross-level interactions are investigated to examine variations by grade. Results suggest that all SC indices except T-units per sentence exhibit varying growing trends. The results align with Biber's hypothetical stages of syntactic development, indicating learners’ progression toward greater subordination and phrasal complexity. Negative cross-grade interactions suggest that lower-grade students show heightened improvements in phrasal sophistication over time. The study portrays the developmental patterns of SC within and across grade levels, highlighting both group trends and individual variability in language development. It conceptualizes SC as a multidimensional construct and informs more precise measurement of SC features in writing assessment and instruction.