This article presents data from a research study designed to compare the achievements of teenagers with Down syndrome educated in mainstream classrooms or in special education classrooms throughout their full-time education. Progress is reported for speech and language, literacy, socialisation, daily living skills and behaviour. For all the teenagers, there is evidence of progress with age on all the measures except for communication. Communication continued to improve through teenage years for the included children but not for those in special education classrooms. There were no significant differences in overall outcomes for daily living skills or socialisation. However, there were large significant gains in expressive language and literacy skills for those educated in mainstream classrooms. Teenagers educated in mainstream classrooms showed fewer behavioural difficulties. Further, comparison with data published by these authors in an earlier study, showed no improvements in school achievements in special education over a 13 year period in the UK (1986-1999). (Contains 4 figures and 29 tables.)