Gathering information on the performance of school principals and acting on the information about their effectiveness as leaders is an essential part of improving school performance. This paper reports part of the findings from an initiative conducted to sustain and improve management quality at secondary schools in Vietnam. An evaluation tool was developed based on Vietnam's professional standards for school leaders and was used by school principals and teachers to provide more insight into their professional practices and training needs. 593 principals and 1647 teachers from 16 provinces across the eight regions of the country participated in the survey and 110 follow-up interviews were conducted. The results indicated that there were certain socio-cultural factors that conditioned the practices of Vietnamese school leaders, including demanding them to be politically, ethically and professionally fit, and to assume many peripheral roles. School principals in Vietnam generally met state standards in terms of qualifications and management expertise, and were perceived to have adequate competencies in handling school management, especially in promoting teachers' teaching capacity and ensuring educational quality. However, Vietnamese school principals found it challenging to manage school resources and assets and to instruct teachers on leadership; areas that they have hitherto received little training in.