Two cohorts of French immersion students in a British Columbia school who were entering Grades 4 and 5 respectively participated in the study and were each tested at the end of Grades 5 and 7. The Grade 4 cohort followed the newly introduced 80% French, 20% English language (high intensity) program, while the Grade 5 students followed the 50% French, 50% English language (low intensity) program. Compositions written in Grades 5 and 7 by each group were analysed and compared in regard to the lexical, grammatical and discourse development. Results showed an increase in the quality of writing between the beginning of Grade 5 and the end of Grade 7. However, students from the cohort who received a higher intensity of French instruction did not achieve any better in vocabulary, grammar and discourse development than the students in the low intensity group. The results showed a plateau effect between Grades 5 and 7 for only two of the variables investigated: vocabulary diversity and frequency of time markers. Moreover, apart from the percentage of correct prepositions, there was no difference in the writing quality of the two Grade 7 groups based on level of intensity.