Assessment measures of oral reading fluency can be applied by teachers or education professionals and help to provide an overview of the academic development in reading of each student; and when these simple measures are systematically applied over time, they can be used to track a student's possible difficulties. Aim: This study aimed to monitor the development of oral reading fluency in students from the 2nd to the 5th grade of Elementary School I during the school year. Method: This study was approved by the research ethics committee (09575419.0.0000.5406) of the home institution. The study included 400 students from the 2nd to the 5th grade of Elementary School I from a municipal public school in the interior of the State of São Paulo, aged from 7 years to 10 years and 11 months. The Performance Assessment in Reading Fluency was applied. Reading fluency measures were performed by collecting oral reading of three texts of the same textual complexity in the months of March, July and November. For the analysis of each text, the analysis parameters of the types of errors made during reading were used, referring to words read correctly and incorrectly per minute. Results: The results were statistically analyzed using the Statistical Package for Social Sciences, version 22.0, with a significance level of 5% (0.050). With the application of the Wilcoxon Signed Rank Test, it was possible to verify that there was a statistically significant difference in the groups of this study both for the total number of words read correctly in one minute and the total number of words read incorrectly between the third moment of the fluency measure in comparison with the first moment. With the application of the Mann-Whitney Test, it was possible to verify that there was a statistically significant difference, indicating that the groups had a lower number of words read correctly per minute in the first reading measure compared to the second and third measures. This same finding was found in the reading of misspelled words per minute. Conclusion: The results of this study allowed monitoring and accompanying in a simple, reliable and valid way, the progressive development of oral reading fluency, evidenced by the increase in the number of words read correctly and the decrease in the number of errors from the 2nd to the 5th grade of Elementary School I.