We investigated U.S. state and national trends in the enrollment of students ages 6 to 21 years under the specific learning disability (SLD) category across 15 consecutive school years (2005-2006 to 2019-2020). We used multi-level modeling to estimate the effects of state and time on SLD enrollment and conducted a policy analysis of three states (Rhode Island, Kansas, and New Mexico) to examine changes in SLD policy (including Response to Intervention) in conjunction with trends in enrollment. Results indicate significant differences in SLD enrollment between states in the initial year and significant decreases in SLD enrollment over time, but no significant differences in the change in SLD enrollment between states. Results from the policy analysis suggest that the state policy context (including legal requirements in the SLD evaluation process), type of RTI model, and method of SLD evaluation can affect SLD enrollment. We discuss these results within the context of increased variability in RTI models.