<p>Studies have shown that teachers’ knowledge of language and literacy concepts is a significant predictor of students’ reading performance. However, it is also possible that students’ reading performance predicts future teachers’ knowledge. Thus, in this study, we aimed to examine if teachers’ knowledge of language and literacy concepts and students’ reading performance are reciprocally related. Eight hundred and twenty-nine Grade 3 to 9 students (48% female; <i>M</i>_age = 10.5&#xa0;years at first measurement point) from British Columbia, Canada, and their 43 language arts teachers (82% female) were followed from the beginning to the end of the school year and were assessed twice. Students were assessed on the Test of Word Reading Efficiency-2 and on the Test of Silent Reading Efficiency and Comprehension. The teachers completed a survey on their knowledge of phonological awareness, phonics, and morphology. Results showed that teachers’ knowledge of language and literacy concepts predicted the end-of-the-year students’ reading performance even after controlling for teachers’ years of teaching experience and students’ reading performance at the beginning of the school year. In contrast, students’ reading performance at the beginning of the school year was not a significant predictor of teachers’ knowledge at the end of the school year. Taken together, these findings challenge the assumption that teachers’ knowledge and students’ reading performance influence each other’s development.</p>