In 1990 the Kentucky legislature passed the Kentucky Education Reform Act (KERA). The law mandates the use of performance-based assessments, including portfolios in mathematics and writing. This paper presents findings of a case study of a fourth-grade classroom teacher's experiences in implementing instructional changes to help students produce writing-assessment portfolios. Data were obtained through participant observation, interviews, and document analysis. The use of writing portfolios changed the way in which the teacher viewed writing in the classroom; everything became connected in some way to writing portfolios. The teacher adapted more easily than other teachers to the changes partly because she was pursuing an advanced degree in education. She was frustrated, however, with the brief teacher-preparation time, training that focused on assessment, lack of time for student writing, and the state grading system. A conclusion is that assessment is driving instruction, as happens with standardized testing. Other issues to consider are the definitions and purposes of portfolios, student ownership, and scoring procedures. (Contains 25 references.) (LMI)