Readability Indices and Students’ Achievement in Comprehension: A Content Analysis of Passages in English Textbook for Study of Oyo State Public Senior Secondary Schools

In this study, the researcher found out the relationship between readability indices and students achievement in test. Readability and comprehension test on selected passages from the English Language for Senior Secondary School Book 2 were conducted among students; content analyses of the same passages were equally carried out. The outcome of the content analysis showed that the degree of lexical density and synthetic complexity of the passages are very high while the result of the readability and comprehension test showed the correlation coefficient(r) of 0.890 which indicates a strong positive relationship between readability indices and students’ achievement in comprehension test. Base on this, it was recommended that English language textbook for public schools should be guided by a comprehensive readability test and that government should consider whether or not the recommended textbooks are appropriate for the target students before recommending them, instead of using political or social influence of the authors and the publishers.