Three pilot studies--effects of writing prompt modality on writing performance; effect of topic familiarity; and effect of topic, sample and rater group membership on the stability of scoring criteria application--are used to identify the variability in student writing performance. A writing competency test aims to assess writing-specific skills and, in preparation for a study of the effects of writing prompt modality on essays written in two modes of discourse, this investigation identifies essay scoring criteria sensitive to probable effects of the different modalities. The following scoring criteria are identified: (1) Do the different writing modalities affect essay writing on Analytic Expository Scale subscales? Do differences occur on the General Impression, Organization, Support, and Total Score ratings? (2) Does prompt modality affect essay length? (3) Does prompt modality influence the number and types of facts included in the essay? and (4) Does prompt modality affect syntactic fluency? Since the final study examines eighth-grade writing performance, the pilot study examines the appropriateness of an analytic scoring rubric previously employed with high school and college level writing. Sample essay topics and rating formulas are also included. (CE)