Demographic and institutional factors responsible for the large variations of student retention and achievement at further education (FE) colleges throughout the United Kingdom were examined. Data from individualized student records were analyzed, and 10 FE colleges identified as serving areas of deprivation were visited to assess the extent to which demographic factors are the main determinants of differences in rates of retention and achievement and to identify institutional practices connected with higher and lower retention and achievement. Although demographic differences in student profiles had an impact on the relative rates of achievement recorded by different colleges, demographic make-up of student bodies did not appear to explain the major part of interinstitutional variations in achievement. A substantial part of the achievement gap appeared to stem from factors lying within the direct influence of FE colleges. A total of 53 key characteristics associated with effective interventions to raise student achievement were identified. The characteristics involved the following aspects of practice: strategic commitment; collegewide approaches; recruitment, placement, and induction; design and delivery of curriculum; tutorial and other support; teaching and pedagogy; and monitoring, evaluation, and follow-up. It was concluded that more work is required to determine how demographic factors act as barriers to achievement. (Contains 12 references.) (MN)