This quasi-experimental study explored a response-to-intervention (RTI) design in which Tiers 2 and 3 were inverted for the most at-risk first grade students in reading intervention in seven classrooms (n = 24) across two culturally diverse schools. These students were matched using propensity scores and compared to a second group of first grade at-risk students for reading difficulties who received a traditional RTI intervention program (n = 24) from 12 classrooms across nine culturally diverse schools in the same southeastern city. Interventions were identical with the exception of the RTI tier inversion. The intervention largely emphasized word-level reading skills, with focus on letter-sound correspondence, sight-word recognition, and decoding, and also included spelling and fluency. Statistically significant effects were found for the intervention on word reading measures; however, differences for decoding measures were not found to be statistically significant. Given that the decoding assessments had effect sizes of .025 (small) and .037 (medium), a larger sample may demonstrate a significant positive impact of udRTI on these measures as well. Implications for continued study with the udRTI model are discussed.