Procedures Pupil performance was assessed under baseline and intervention conditions for a total of 4 weeks. This resulted in an A-C data-based, case study design. This particular design cannot establish a functional relationship between the use of PECS and pupil outcomes, but it can be used to evaluate the effectiveness of specific interventions over typical teaching procedures (Kennedy, 2005). During baseline sessions, instructional sessions were conducted with the teacher and teaching assistant using typical or normal instructional procedures. For the most part, baseline instruction consisted of discrete trial learning sessions in which some form of stimulus (e.g., directive, request, and verbal prompt) was provided to students. If they
