This study aimed to design and validate a questionnaire addressing factors which underline the characteristics of acquisition of English language in EFL classrooms and explore the relationship among the underlying factor of the questionnaire, the characteristics of teachers and Grade Four Senior High School (G4SHS) studentsí achievement in EFL classrooms. To this end the 41-item English Language Acquisition Scale (ELAS) was designed by the researcher and administered to 518 G4SHS students. Also, to find the relationship among the ELAS, its latent variables, factors underlying English teachersí attributes in EFL classes and students Ďachievement 126 participants were randomly selected out of population to answer the 102-item English Language Teachersí Attribute Scale (ELTAS) and a Schema-Based Cloze Multiple-Choice Items Test (SBCMCIT) respectively. The results showed that the ELAS consists of five factors, that is, Learning booster, contribution, Engagement, Orientation and Criterion. When the ELAS and its underlying factors were correlated with ELTAS and its sub-constructs not only the scales themselves but also their underlying factors showed significant relationships with each other. Also, the ELAS and its underlying factors showed significant relationship with English achievement scores.Keywords: language acquisition, teacher effectiveness, language achievement.