The purpose of this study was to examine the effects of streaming and non-streaming on the personality, and social and intellectual development of junior school pupils. The data are held under nine separate study numbers; one for each of the eight surveys and one for the merged file. The study covers a four-year period. In the first year, 1964 (Surveys SN:008 and SN:009), a cross-sectional study of 84 schools, 42 matched pairs of streamed and non-streamed schools, was made. In the succeeding three years, this number was reduced as schools dropped out due to changes in organisation or to reductions in numbers of pupils or staff. In the end, only schools that had completed the full research programme were considered in the longitudinal study, that is, data from 72 schools or 36 matched pairs. The longitudinal study was concerned, therefore, with those children who were in their first year in 1964 and who remained in the school throughout the whole of the junior course - 5521 pupils in all. The data are of two main types, those concerned with pupils and those concerned with teachers. SN:261 is a merged file of datasets for pupils (SN:007, SN:008, SN:010, SN:012).