An exploratory study that involved two male and two female elementary students with attention-deficit/hyperactivity disorder (ADHD) was carried out in homeschools and public schools. The general purpose of the study was to determine whether parents could provide instructional environments that facilitated the acquisition of their children's basic skills over time. Students were observed using the Mainstream Version of the Code for Instructional Structure and Student Academic Response (MS-CISSAR), an eco-behavioral direct classroom observation instrument that produces information on ecological, teacher, and student behavior processes. Pre and post standardized achievement test scores and rate-based measures were analyzed to determine gains in reading and math for all students. The results indicated that homeschool students were academically engaged about two times as often as public school students and experienced more reading and math gains. The key variable appeared to involve student to teacher ratios that existed between the two settings.