The purpose of this randomized control trial (RCT) was to examine the impact of one-to-one high-dosage tutoring on reading achievement of kindergarten and first grade students, many at risk of reading failure. This nearly two-year study collected reading assessment data from 185 students, from across 13 classrooms, randomly assigned to either the one-to-one high-dosage tutoring group or the teacher-instruction-only group. Treatment students received tutoring support 2-3 times per week across the school year from specially trained tutors using a digital literacy platform. Tutoring focused on sequenced skills beginning with letter identification and sounds and moved to reading stories. The results of the Hierarchical Linear Modeling (HLM) analysis, from both Chapter One assessments as well as the nationally recognized assessments, indicate that Chapter One's high impact tutoring program is highly effective in helping at-risk kindergarten and first grade students achieve reading proficiency. Tutored students outperformed non-tutored students on multiple measures of reading achievement.