In the present study two EFL (English as a Foreign Language) teaching methods were compared: the communicative approach (CA) and the grammatical approach (GA). In the CA, grammar was not directly taught or explained. On the other hand, in the GA, grammar was directly taught and frequently supplemented by some explanations in Japanese. The purpose of this study was to clarify how much differently these teaching approaches might affect students' acquirement of linguistic skills. Ninety fifth-graders were divided into two of the above mentioned instructional conditions. For each method there were 4 classes, each one taught by a different teacher. The total teaching time was 20 hours. Data for one class were not included in the final analysis due to experimental contamination. The results indicated that (1) GA students performed better in grammatical ability post test and in reading ability test 2 months later; (2) For the immediate post test, significant ATI (Aptitude Treatment Interaction) were found on several aptitudes, especially on intelligence, suggesting that GA would capitalize on as CA would compensate for intelligence. However, after a 2-month period, the pattern of ATI was found changed.
