Introduction

This chapter first describes the limitations of observational studies. Then it covers some theories that can help us understand the impact of schools on young people. The Learning Together intervention is described, and evaluation of programme delivery and impacts is discussed.

The limitations of observational studies

Chapter 3 described evidence of statistical associations between, on the one hand, various measures of school-level characteristics and, on the other, various risk behaviours and health outcomes among the students attending these schools. The best of these studies used longitudinal designs tracking students over time so that it was clear that the school-level characteristics in question were present before, and therefore could plausibly be a cause of, the student risk behaviour or health outcome. These studies also tried to adjust statistically for possible ‘confounding’ factors that could provide alternative explanations for why students in certain schools engaged in more risk behaviours or had worse health outcomes. These confounders might be characteristics of the students who attended the schools, their families or the neighbourhoods where they lived. Such studies provide quite plausible evidence that schools might influence their students’ involvement in risk behaviours and health outcomes.

However, these studies are still quite limited in what they can tell us about school effects and the three toxic mechanisms. Some of the studies were cross-sectional, and with these it is hard to know whether the school-level factor in question is the cause or the consequence of the risk behaviour or health outcome.