Abstract
The current research is a longitudinal study that probes how speaking performance of senior high school students changes across a year (specifically 13 months) from the first year to the second year at an English Course at a Super English Language High School (SELHi). Thirty-nine Japanese learners of English (20 male and 19 female students), who were frequently exposed to English input and often used English, took a speaking test of picture description twice. Analyses of their utterances show substantial progress in speaking performance. To be specific, all the aspects tested in syntactic complexity and lexical complexity changed to a moderate or large degree. In addition, there was also improvement in some aspects of the number of uttered words and speaking time, fluency, and accuracy (e.g., an increase in the proportion of error-free clauses).
