The Common Core State Standards (CCSS) require students to read grade-level text with "scaffolding as needed." The current study examines the effectiveness of interactional scaffolding, which is responsive in-person support an expert provides to a novice reader in order to support the reader's comprehension during reading instruction, for 213 young adolescents learning within a four-lesson small-group guided-reading intervention (N = 196 instructional sessions). The intervention taught students, many of whom were reading below grade level, to use comprehension strategies as they read CCSS-style complex texts. To support student reading, tutors were encouraged to choose from a set of interactional scaffolds to contingently respond to student needs as they arose. Multilevel regression indicated that motivational scaffolding--but not vocabulary, fluency, comprehension or peer scaffolding--predicted growth on standardized reading comprehension. Implications for research and practice are discussed.