Key messages

• Schools and their staff are able to better implement interventions to address students' healthy eating, physical activity, obesity, and tobacco or alcohol use, when strategies are used to support them to do so.

• More research is required to understand which individual strategies are the best for supporting schools and their staff to implement these interventions.

• No unwanted effects of providing implementation support to schools have been identified in the studies to date, and information about their cost is limited.

What did we want to find out?

We wanted to find out how effective strategies were in supporting the implementation of school‐based interventions to address diet, physical activity, obesity, tobacco use and/or alcohol use in students (aged 5 to 18 years). For example, whether education and training of school canteen operators (implementation strategy) can improve the implementation of a healthy canteen policy (intervention) to reduce availability of unhealthy food (implementation outcome) and improve student diet. We also wanted to know if they had any adverse effects and if they were cost‐effective. Other examples of strategies include methods of improving quality, feedback on how the school was doing, prompts and reminders, and educational resources (e.g. manuals).

What did we do?

We updated a previous search that we had conducted for trials that compared the use of a strategy to support intervention implementation to those that had not, or that had compared two or more different implementation strategies. The trials looked at strategies to support the implementation of interventions in schools that addressed student diet, physical activity, obesity, tobacco use and/or alcohol use. We compared and summarised the results and rated our confidence in the evidence, based on factors such as trial methods and sizes.

What did we find?

We found 14 new trials to add to those identified in our previous search, bringing the total number of included trials to 39 with 6489 participants. Most were conducted in Australia and the USA and most examined strategies to implement healthy eating and/or physical activity interventions. We found, compared with a control, that the use of implementation strategies probably results in large improvements in the implementation of healthy eating, diet, physical activity, obesity, tobacco use and/or alcohol use interventions in schools. An increasing number of trials assessed potential adverse effects for schools, staff or students and none identified any adverse effects. A number of trials assessed the economic benefits of the use of intervention implementation support strategies; however, the results were inconclusive.

What were the limitations of the evidence?

Despite our review showing that the use of implementation strategies probably results in large improvements in programme implementation, the trials used methods likely to introduce errors in their results and were primarily conducted in two countries (Australia and USA). As a result, we are moderately confident that strategies to support implementation improve the implementation of these interventions in schools.

How up to date is this evidence?

We searched databases between 1 May 2021 and 30 June 2023.