This paper discusses how the Coh-Metrix system was used to measure readability levels of comprehension texts used by the teachers of English for classroom instruction at a junior secondary school. The researchers wanted to determine if the comprehension texts match the readability level of students at this level of education. This is important because all the students at the school are not native speakers of English. Therefore, they are learning English as a Second Language (ESL). However, the authors of the majority of the English textbooks used in schools are native speakers of English.The study was qualitative in design and five (5) comprehension passages used by English Language teachers for assessment purposes were selected for this study. The data derived were analysed qualitatively. The results showed that random selection of English Language comprehension texts without subjecting them to a readability test such as the Coh-Metrix may compromise the quality of learning. The results also showed that the readability level of textbooks may contribute to the poor performance of ESL learners and other subject areas.