This 2003 study from The UK's National Foundation for Educational Research evaluates the effectiveness of six Alternative Education Initiatives (AEIs).  Effectiveness was measured by success in returning pupils to mainstream education, educational attainment, post-16 outcomes and reducing anti-social behaviour, including offending.

The study concluded that AEIs offer

"a distinctive holistic package of sustained pastoral support and alternative curriculum opportunities to which the majority of their students respond positively. Nevertheless, the findings ... [indicated] ... that the pupil clientele also contains a number of young people who do not succeed at AEIs. The range (and severity) of damaged youngsters being allocated to such provision, combined with the limited resources available, may largely account for this lack of success."

The study recommends increased (and sustained) funding to allow AEIs to deliver the intensive support that young people attending them require.

You can read the summary at: http://www.nfer.ac.uk/research-areas/pims-data/summaries/an-evaluation-of-alternative-education-initiatives.cfm.

Or download the full report: http://www.dfes.gov.uk/research/data/uploadfiles/RR403.pdf.