Final answer:
The primary advantage of a student portfolio is that it measures student achievement over time and allows for a comprehensive view of learning.
Step-by-step explanation:
The primary advantage of a student portfolio as an alternative to traditional tests and measures is that it measures student achievement over a long span of time. Portfolios allow students to showcase their work and progress over a period rather than being limited to a single test or assessment. They can include a variety of assessments and authentic assignments that provide a more comprehensive view of student learning.