Synthesis: Instruction and Professional Development
The inclusion criteria for studies in this part are consistent with the inclusion criteria established for the volume as a whole. However, as specified in chapter 1, the criteria for chapter 14 (language of instruction) differ in several ways from those used in other chapters. For example, it was essential that chapter 14 be consistent with previous reviews of studies that compared bilingual instruction with English-only instruction, but this criterion required a longer time frame. Thus, studies reviewed in chapter 14 include studies conducted earlier than 1980. In addition, the programs cited in studies in chapter 14 included at least a 6-month span between the onset of instruction and posttests to ensure a program had actually been implemented; in these cases, most treatment durations were of at least 1 year.