The purpose of the current study was to examine the skill-by-treatment interaction (STI) framework to intensify reading interventions. The effects were tested with a multiple-baseline across-participants single-case experimental design with a contraindicated phase. Four students in second through fourth grades were the participants for the study. All four had received a tier two reading intervention that focused on phonics but did not show sufficient growth from the intervention. The intervention was then modified based on the phase of learning and the Fuchs et al. (2017) taxonomy for intervention intensification. The contraindicated intervention led to negligible or negative effects for all four students (between-case standardized mean difference = -0.61, 95% CI = -1.24 to 0.02), but the indicated intervention led to a large effect on the reading outcome measures across the four participants (between-case standardized mean difference = 1.18, 95% CI = 0.42 to 1.95). Thus, the contraindication design showed an experimental effect for matching interventions to student skill within an STI framework.