Because traditional performance measures may not accurately assess what students learn or are taught, some K-12 classroom teachers, states, and teacher preparation programs are beginning to use portfolio assessment to document learning and growth in learning over time. Portfolio assessment is considered a more authentic way of evaluating and establishing student progress throughout the learning process, and of showing the relationship between classroom performance and performance in "real" situations. Many educators see portfolios as one of the better ways to get students to invest in their learning and to provide an adequate portrayal of how students' learning improves or changes over time. Concerns with portfolio assessment include: the amount of time required to review portfolios and furnish worthwhile feedback; the difficulty of establishing reliability and validity; and the "authenticness" of portfolio assessment itself. Portfolio use in the education programs at five institutions is examined: Central Washington University, Jacksonville State University (Alabama), Montana State University, Saginaw Valley State University (Michigan), and SUNY-Plattsburgh (New York). The paper concludes with a discussion of faculty and student perceptions on the use of portfolios. (Contains 17 references.) (ND)