This study compared PISA 2009 student reading literacy scores with principal perceptions across three countries with varying levels of student performance: Korea, Mexico, and the United States. Seventy-five countries participated in PISA 2009, which measured 15-year-old children's reading achievement and principal perceptions. The study explored the relationship of principals' perceived levels of leadership, school autonomy, and use of test results with student attainment of reading literacy. School variables were treated as covariates when each effect of principal leadership was interpreted. All variables were included in a multilevel model and analyzed simultaneously. The means and standard deviations of outcome variables and the explanatory and control variables for the model of the study were calculated by taking into account sampling weights, as well as plausible values for reading literacy scores. SAS PROC MIXED was used to fit hierarchical linear models for the study. There was a positive relationship between student achievement in reading literacy and testing to improve instruction in all three countries--Korea, Mexico, and the United States--and there was a negative relationship between student achievement and lack of resources. Social, economic, and cultural status showed a positive relationship with reading literacy. To be specific, testing to improve instruction can be beneficial in all three countries when it is defined as using tests to group students for instructional purposes and to identify aspects of instruction or the curriculum that could be improved. Results also indicate that students are likely to achieve better if principals perceive that there are no shortages of personnel and equipment. (Contains 6 tables and 1 figure.)