range of environments, including classrooms, homes, clinics, and community settings. The programs also vary on dimensions of environmental stimulation, with traditional behavioral programs generally conducted in distraction-free settings and more naturalistic procedures being implemented in more “everyday” environments. However, even in the most natural environments, it is common that the curriculum specifies certain environmental arrangements. For example, the early Denver classroom was described as being “choreographed” in a manner that reflected precise planning and coordination of physical space, equipment, materials, activities, staff roles, and timing (Rogers and Lewis, 1988).
Consistent across programs is the existence of predictable daily routines, which are organized according to written schedules of activities. The center-based programs tend to vary activities from one-to-one to small group to large group, with goals addressed in the most compatible format (e.g., new language can be difficult to teach in a large group situation). For center-based programs, the class size varies from 6 (Denver) to 18 (Walden prekindergarten), although there is variability across children’s ages. Class size also varies, depending on the ratio of children with special needs to total number of children (e.g., the Walden preschool program has 18 children, but only 6 have autism).
Perhaps more relevant than the number of children with autistic spectrum disorders is the adult:child ratio, which all of the programs keep high in order to ensure that each child’s individualized needs can be met. Across the ten programs, the adult-child staffing ratios range from 1:1 to 1:8, depending on the program format, class size, and children’s developmental and chronological age. The Developmental Intervention Model and the Young Autism Project remain nearly exclusively 1:1 throughout the intervention period, including the use of a one-on-one “shadow” if a child is eventually included in a regular early childhood center. Other programs offer staffing of approximately 1:3, although each of these provides for some 1:1 sessions in the course of each child’s day. A number of programs (e.g., Children’s Unit, Douglass, Walden) systematically and intentionally fade the adult:child ratios across time in intervention, in order to prepare children to function independently in future sites.
All ten programs explicitly address the communication irregularities associated with autistic spectrum disorders, although there is some variability in the specific target objectives and in the strategies for promoting communication. The programs also target other developmental domains, including engagement, social, play, cognitive and academic skills, self-help, behavioral challenges, and motor skills. The distribution of treatment time devoted to teaching skills in different developmental areas