Students who do not develop adequate literacy skills are at higher risk for school dropout and face inferior labor-market options (National Governor’s Association, 2005; Vignoles, De Coulon, & Marcenaro-Gutierrez, 2011). Existing evidence suggests that the transition from elementary to middle school is a particularly crucial period for a child’s literacy development and requires sustained support through this transition (Chall & Jacobs, 2003). I capitalize on the existence of a natural experiment born out of one school district’s use of an exogenously-determined cutoff in Iowa Test scores in 5^th grade to assign students to a “double dose” of literacy instruction in middle school. My findings suggest that, on average, this district-delivered, research-driven instructional intervention generates modest immediate increases in students’ state standardized reading and mathematics test scores (0.2 SD) in 6^th grade, and positive medium-term effects (3 percentile points = 0.15 SD) on their Iowa Test percentile rank in 8^th grade. This latter impact is particularly important, since some studies have examined the tendency for instruction to focus narrowly on material tested for accountability tests, but that performance improvements on these assessments may not generalize to others.