Effective school leadership in supporting outcomes for all students is critical. This study focuses on six New Zealand principals as they endeavour to make a difference to reading outcomes for 11 to 13 year-old students. In New Zealand, there are approximately 20% of students who are underachieving in reading. Once they reach the final years of primary schooling, this is the final opportunity to rectify this underachievement before these at-risk students enter secondary schooling. Interviews were conducted with the six principals at six case study schools, which represented a range of schools. Findings showed that there was widespread use of standardized testing results in reading to provide accountability for the New Zealand National Standards requirement, and also to inform next teaching steps. However, principals differed in the manner that they led the schools-wide analyses of the data. There was a stark diversity in the implementation of sustained and focused professional development in reading. The use of teacher aides to support our most vulnerable students, low-progress readers and English Speakers of Second Language was widespread, with only two schools providing in-school support and training of these paraprofessionals.