Work is reported towards the completion of a prototype duplex-design assessment instrument for grade-12 science. The student course-background questionnaire and the pretest section of the two-stage instrument that was developed were administered to all 134 12th-grade students at St. Clairsville High School (Ohio). Based on the information obtained from the first-stage form, a second-stage form was prepared and adapted to the course level and background of each student in each of four science areas: (1) earth sciences; (2) biology; (3) chemistry; and (4) physics. Second-stage testing plans were made for statewide testing in 40 Ohio schools in March and April of 1991. Additional open-ended items were sought to complete the six forms of the instrument. Two papers on the present stage of the project are provided: "Individualized Educational Assessment: Twelfth-Grade Science" (R. Darrell Bock and Michele Zimowski); and "The Graded Mark-Point Method of Scoring Performance Exercises and Open-Ended Items" (R. Darrell Bock). The questionnaire and pretest from the pilot administration, and individualized test booklets representing four levels of difficulty in the second-stage forms are included. (SLD)