The rising rates of high-risk behaviours, such as substance abuse, unsafe sexual practices and violence in South African schools, have accentuated the need for intervention and prevention programmes in the education system. High-risk behaviour is related to changes and uncertainties at community level. The traditional values and behavioural codes are undermined and there is no corrective action from the community to control this behaviour. This study describes the need for support of adolescents, who are in a state of development and change and whose abilities are increasingly being tested by stress factors from a rapidly changing environment. To meet these needs for support, an experimental peer support programme was implemented in schools. Peer support involves the provision of information about healthy lifestyles and high-risk behaviour, such as substance abuse, crime and HIV/AIDS-related aspects. Through peer support, healthy lifestyles can be modelled, and a forum for the discussion of problems established. Peer supporters can assist their peers in dealing with problems and a context can be created in which new and healthier behavioural patters can develop. Peer support is important because educators and teachers are unable to manage the large number of learners who are experiencing problems and schools offer limited professional psychological support to learners. The objectives mainly entailed the prevention of high-risk behaviour related to HIV/AIDS, crime and substance abuse, as well as the enhancement of learners’ psychological well-being and the social climate in schools. The peer support system was implemented in four experimental schools and four similar schools served as a control group. The schools involved were selected by means of a stratified sampling method. A total amount of 2045 respondents between the ages of 12 and 21 years participated in this study. The peer support system was evaluated in terms of a pre and post-measurement in order to determine the impact of the system on the schools and learners in the schools, and to determine whether the set objectives have been achieved. The hypothesis was that the peer support system would have a positive effect in reducing high-risk behaviour and improving the psychological well-being of learners. A questionnaire was used as a pre and post-measurement tool to determine whether there had been significant changes and/or improvements regarding high-risk behaviour, crime, school climate and psychological well-being in the school system. The experimental and control school communities were compared. Significant differences were found between the experimental group and the control group in terms of behavioural problems in the school, school climate, high-risk sexual behaviour and psychological well-being. Learners’ perception of problem behaviour in the school remained unchanged in the experimental group, whilst the control group’s measurements became statistically significantly (p<0,05) more negative over time. A statistically significant difference at the 5% significance level was found between the control group’s pre and post-measurements regarding learners’ experience of the school climate. The control group’s experience had become more negative at post-measurement, whilst the experimental group’s experience had remained unchanged over time. A statistically significant difference was found between the experimental and control groups (p<0,001) in respect of the level of sexual experience. The number of sexually experienced learners in the control group had increased at post-measurement, whilst the level of learners’ sexual experience had remained constant in the experimental group. Furthermore, a significant increase (p<0,001) was found in the level of sexual activity among the control group during the last 30 days, but not in the experimental group. This implicates that the intervention has had a preventative effect that counters the normal tendency of increased sexual activity with age. More than 60% of learners viewed their friends as sexually experienced. The perceived group norm for the experimental group remained the same over 18 months, whereas a significant increase (p<0,001) was found in the control group. No decrease was found in the psychological well-being of learners in the experimental group at post-measurement, whereas that of the control group had decreased significantly (p<0,05). No statistically significant differences were found for substance abuse and personal control of risk among learners. Although many other variables could play a role in these changes, the conclusion can be made that the peer support system probably had a preventative effect in schools. The study further indicates that approximately two thirds of all learners had been aware of the system and about 40% had used it. The peer system was generally evaluated as positive and the biggest problems were related to the implementation and organization of the system, as well as the confidentiality of information. Recommendations have been made regarding the improvement of project implementation. If enhanced co-operation from school staff can be obtained during implementation of the intervention, the peer support system could function better and a bigger impact in schools could be achieved. In conclusion, it is important that intervention programmes be promoted efficiently in schools in order to facilitate optimal functioning. / Dissertation (MA (Research Psychology))--University of Pretoria, 2006. / Psychology / unrestricted