Rapid Phonics is a synthetic phonics intervention intended to improve decoding skills and reading fluency. It teaches the relationship of word sounds to their corresponding letter groups in a structured way. In this evaluation, the intervention was delivered across the transition between primary and secondary school to Year 6/7 pupils who had not reached Level 4b in English at the end of Key Stage 2. Rapid Phonics pupils received one-and-a-half hours of tuition per week, in groups of four or fewer, by specialist teachers from Norfolk County Council. The intervention was delivered over six weeks in the summer term of 2013 (end of primary school) and six weeks in the autumn term of 2013 (start of secondary school) to 201 pupils from 22 primary schools and then in 13 secondary schools across Norfolk. Pupils were individually randomised to receive the intervention or to a waitlist control group, who received the intervention at the end of the trial. Key conclusions include: (1) Rapid Phonics was not found to have a noticeable impact on the primary outcome measure of reading comprehension at the end of the intervention; (2) There was a small improvement in the secondary outcome of decoding, but this did not reach statistical significance; (3) Conducting the intervention during the last term of Year 6 and the first term of Year 7 was not the most settled period as there were many disruptions in the school environment and conditions may not have been best suited for the children to respond optimally to tutoring; (4) Continuing the intervention from primary to secondary schools can be logistically problematic, with a number of children transferring to schools outside the project or changing secondary school soon after arrival; and (5) An area of further research would be to employ the intervention in one continuous period at an earlier point in primary school, using a larger sample size and with more focus on children receiving free school meals and upon SEN. No positive effect size was found for the primary outcome of reading comprehension. A small positive effect size was found for the other secondary outcome of non-word reading, but not for the secondary outcome of single word reading. None of the measures were found to be statistically significant, suggesting that there is not sufficient evidence to confidently conclude that the observed effect was caused by the programme rather than occurring by chance. As a result, it is not clear that Rapid Phonics is an effective intervention for improving reading comprehension for pupils who have not achieved the expected level of attainment in literacy at the end of primary school, when delivered across the primary/secondary transition.