The studies reported here focus on the effects of mode of administration of the Massachusetts Comprehensive Assessment System (MCAS) in grades 4, 8, and 10. These studies, which draw on earlier studies, also examine the mode of administration effect at different levels of keyboarding speed and for students who received special education (SPED) accommodations in the classroom. Also explored were mode of administration effects for AlphaSmarts and eMates, two portable writing devices. Study participants included 152 4th graders, 228 8th graders, and 145 10th graders who were randomly assigned to write their MCAS essays on paper or on the computer. Essays were scored by teachers and advanced graduate students using MCAS scoring materials, with handwritten essays transcribed and printed on the computer so that scorers would not know whether the essay was originally written by hand or not. Overall, students performed significantly better when they composed essays on the computer. Students who performed both the Language Arts Composition and open-ended questions on the computer scored 4 to 8 points higher on a scale ranging from 200 to 280. The effects were about the same in all grades, but it appeared that students receiving special education services for language arts benefited even more from computer use. (Contains 26 tables, 8 figures, and 56 references.) (SLD)