Units of Sound (UofS) is a computer-based program designed to help struggling readers with their reading and spelling skills. It is a structured, multisensory program that covers reading and spelling from simple phonics skills through to adult reading levels. It involves a high level of independent work by the student, with small groups of students supervised by a teacher or teaching assistant. Each "unit of sound" (or phonic code) is introduced separately, then used in words, and then sentences. This evaluation assessed the reading ability of 786 Year 7 students in 45 schools. Students were randomly assigned within the schools to receive the intervention if they had scored below Level 4 on their Key Stage 2 National Curriculum assessments (aka SATs). Students spent one 60-minute session with the teaching assistant present and a further 30-minute session on another day working independently on the material covered with the teaching assistant. Schools varied in how they allocated the time. The intervention lasted for 18 weeks. Students were evaluated at baseline on the New Group Reading Test (NGRT) and then at follow-up on the NGRT and the Single Word Spelling Test (SWST). A light-touch process evaluation was conducted to determine teaching assistants' and students' perceptions of the program. This included surveys of teaching staff and students and interviews with the DA coaches. Key conclusions from the evaluation were: (1) This attempt to evaluate the UofS program was severely compromised and no firm conclusions can be drawn from it; (2) Schools need dedicated staff and better ICT support in their school if they are to implement UofS; (3) Students in schools that participated in the distance-learning-only support seemed to perform similarly to those who received face-to-face support; and (4) More research with better recruitment, better technology support, and lower attrition would be needed to determine the effectiveness of the program and the generalizability of the effects.