This study examined the effects of integrating extensive reading (ER) instruction on the
narrative essay writing performance of public senior secondary school students in
Gwagwalada Area Council, Federal Capital Territory, Abuja, Nigeria. Employing a quasi
experimental pre-test–post-test non-equivalent groups design, the study recruited 260 Senior
Secondary School Two (SS2) students drawn from two intact classes: an experimental group
(n = 84) exposed to ER-integrated writing instruction, and a control group (n = 76) receiving
conventional essay writing instruction. Performance was assessed using the COEMA rubric:
Content, Organization, Expression, and Mechanical Accuracy, adapted from the West African
Senior School Certificate Examination (WASSCE) marking scheme. Data were analysed using
descriptive statistics and Analysis of Covariance (ANCOVA) at a 0.05 significance level.
Findings revealed statistically significant differences in favour of the experimental group
across all five dimensions of narrative essay writing: overall writing performance, content
presentation, organisation of ideas, language expression, and mechanical accuracy. Post-test
mean scores for the experimental group (71.30) significantly surpassed those of the control
group (34.40), yielding a mean gain difference of 41.4 marks. ANCOVA confirmed large
treatment effects (partial η² = .627). Gender-based t-test analyses further revealed that female
students outperformed male counterparts across all subscales. These findings underscore the
pedagogical efficacy of integrating ER into secondary school writing instruction and advocate
for curriculum-level reforms to embed ER programmes in Nigerian public schools.