Objective: Word recognition, fluency, vocabulary, and working memory have been established as predictors of reading comprehension in the first elementary school grades. However, the additional role of reasoning is not so clear. The aim of this study was to investigate the effect of word recognition, fluency, vocabulary, working memory, verbal, and nonverbal reasoning on reading comprehension, focusing on the additional effect of reasoning when the effects of the other variables are controlled. Method: A group of 159 students from the second and fourth grades was assessed. Results: The results indicated that all variables are correlated with reading comprehension and that the effect size varies according to the school grade. Hierarchical multiple linear regression analyses revealed that in second grade, fluency was the strongest predictor of reading comprehension and that reasoning had no effect on reading comprehension, after controlling for the previous variables. However, in the fourth grade, non-verbal reasoning was the only significant unique predictor of reading comprehension, after accounting for the influence of the other variables. Conclusions: These results highlight the importance of promoting the mastery of accurate and fluent reading in the lower grades while promoting reasoning abilities in the higher grades.

Deficits in oral reading fluency (ORF) impair reading comprehension and tend to persevere throughout schooling. Therefore, the assessment and monitoring of the students' performance in ORF across time should be routinely performed to guide the instruction and intervention. The goal of this work was to develop and validate a test of ORF for Portuguese students from grades 1 to 6 (TAF -Teste de Avaliação da Fluência) that includes specific test forms for each grade level with equated scores that allow comparison across multiple assessment points. In study 1 (N = 1166), the chained equipercentile equating method was performed to equate the test forms' scores horizontally and vertically. The tests of differences performed using the equated scores indicated that they were similar within the same grade level but increased significantly across grade levels.In study 2 (N = 549), reliability and validity evidence for the test forms was collected. Test-retest correlations were higher than .90, suggesting a high stability of the scores. Significant correlations between the TAF scores and the ones obtained in other reading tests, teachers' judgments, and school outcomes, were obtained, thus providing evidence of validity for the developed test forms. This instrument allows not only interindividual comparisons but also the assessment of intra-individual changes in ORF across time or as a result of intervention programs, while avoiding learning effects that arise when the same measure is administered multiple times.