<p>Cognitive flexibility (CF), a core executive function supporting adaptive behavior, has been associated with academic achievement in both reading and mathematics. However, its associations across foundational and higher-order skills, and their developmental variation across domains, remain insufficiently understood within a single unified framework. This study examined grade-specific associations between CF and academic performance in 197 Hebrew-speaking students tracked longitudinally across Grades 3 to 5 (ages 8 to 11), using concurrent structural equation models (SEM) estimated separately at each grade level. Reading fluency and arithmetic fact fluency were examined as potential mediators linking CF to reading comprehension (RC) and arithmetic word problem solving (AWP). A multigroup SEM confirmed that structural pathways were invariant across grades (<i>p</i> = .814), while variable means differed significantly across timepoints (<i>p</i> &lt; .001), validating the grade-specific approach. These models revealed domain- and grade-specific patterns. In Grade 3, CF was associated with RC both directly and indirectly through reading fluency; this indirect pathway was not observed in Grades 4 and 5, consistent with early fluency automatization in transparent orthographies. In contrast, CF showed consistent associations with arithmetic fluency across all grades, which in turn related to AWP and also associated with reading outcomes via cross-domain pathways. CF demonstrated more sustained associations with AWP than with RC, reflecting the extended developmental demands of mathematical problem solving. Together, the findings highlight CF as a domain-general cognitive correlate whose associations with academic skills vary across domains and developmental stages, underscoring the importance of developmentally sensitive approaches to studying CF in learning.</p>