The instrument Samples of Teaching Performance (STP) was developed to assess student teachers' capacity to plan, deliver and evaluate a unit of instruction. The current study reports consequential validity data collected from supervisors (n = 20) and student teachers (n = 62) from three elementary and five secondary teacher preparation programs in Chile that participated in the field-testing of the STP. Student teachers described how this assessment had honed their sense of professionalism and promoted learning of the skills assessed. Supervisors reported enlarging the topics discussed with student teachers and making some changes to the supervisory process. These findings are complemented by an analysis of the STP scores obtained by 24 student teachers, which showed better development of instructional skills when compared to pedagogical reasoning and reflection. These results raise questions about the structure of student teaching to support the implementation of standards-based assessments that entail tasks at different levels of cognitive complexity. (Contains 4 tables and 1 note.)