This longitudinal study examined the effectiveness of a progress monitoring method, namely the Multilayer Instruction Model-Progress Monitoring (MIM-PM), which is a word reading fluency measure. It was used from 1st grade onward to predict the overall reading achievement of students in elementary school by tracking their reading achievement over the following six years. A total of 827 elementary school students in Japan participated in this study. At the end of every other year--2nd, 4th, and 6th grades - a standardized Reading Test (RT) was administered to assess overall reading achievement. The relationship between each MIM-PM measure and RT was determined using the latent growth curve model (LGCM). Using the LGCM, we confirmed that the MIM-PM had an acceptable fit for use in the prediction model for RT from 2nd to 6th grades. The MIM-PM slope explained the intercept of RT, rather than that of MIM-PM. Thus, it can assist in predicting reading achievement in later grades based on word reading fluency, as well as monitor students' progress from an early stage of the educational process.