The Purpose of this study was to examine the effect of grade nine students’ English Language proficiency specifically, reading proficiency, vocabulary proficiency, &grammar Proficiency on their academic achievement. A proficiency test which consisted of 30 reading comprehension, 30 vocabulary and 30 grammar items was administered to the participants to collect data on their English language proficiency. The test was constructed by four English teachers who have been teaching grade nine. Data on academic achievement were collected from 2006 E.C first semester scores of the participants in eight subjects. The participants of the study were 145 grade nine students (79) females and (66) males who were selected by using systematic random sampling. The study mainly employed co relational research design .One sample t-test, the Pearson product moment correlation coefficient and multiple regression were the techniques used to analyze data. Accordingly, the results of correlation analysis showed that students’ academic achievement was positively and significantly correlated with their English Language Proficiency. Moreover, the result of multiple regression analysis showed that students’ English Language proficiency specifically in this study, reading, vocabulary and grammar proficiencies were positive and significant predictors of their academic achievement. Based on the investigation some recommendations were forwarded which mainly focused on raising important points that can facilitate the development and improvement of students’ English language proficiency in order to make them successful in their academic achievement.