Improving the implementation of school-based policies and practices to improve student health

Key messages

• Schools and their staff implement interventions to address student healthy eating, physical activity, obesity, and tobacco or alcohol use better when strategies are used to support them to do so.
• School-based interventions whose implementation is supported may be slightly more effective in improving student healthy eating, physical activity, obesity or tobacco use.
• Most studies do not report economic evaluation of strategies to support implementation of interventions in schools or assess any potential adverse effects.

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 student diet, physical activity, unhealthy weight gain, and tobacco or alcohol use. We wanted to know if they were cost-effective and if they had any adverse effects. Examples of strategies include methods of improving quality, education and training, 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 we had conducted for studies 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 studies had looked at strategies to support the implementation of interventions in schools that addressed student nutrition, physical activity, obesity, or tobacco or alcohol use. We compared and summarised the results and rated our confidence in the evidence, based on factors such as study methods and sizes.

What did we find?

We found 11 new trials to add to those identified in our previous search, bringing the total number of included studies to 38. Most were conducted in the USA and examined strategies to implement healthy eating or physical activity interventions. We found, compared with a control, the use of implementation strategies may result in large improvements in the implementation of interventions in schools, and slight improvements in student healthy eating and physical activity. There was probably little to no effect on student obesity. The effects of implementation strategies on tobacco use are very uncertain. Few trials assessed any economic benefits of the use of intervention implementation support strategies or any potential adverse effects for schools, staff or students.

What were the limitations of the evidence?

Despite our review showing that the use of implementation strategies resulted in large improvements in programme implementation, the studies used methods likely to introduce errors in their results and inconsistencies across included studies, and were primarily conducted in one country (USA). As a result, we have low confidence in the impact strategies to support implementation have on improving the implementation of intervention in schools and most of secondary outcomes (downgraded for risk of bias and variation in methods and results).

How up to date is this evidence?

We searched databases between 1 September 2016 and 30 April 2021.

Authors' conclusions: 

The use of implementation strategies may result in large increases in implementation of interventions, and slight improvements in measures of student diet, and physical activity. Further research is required to assess the impact of implementation strategies on such behavioural- and obesity-related outcomes, including on measures of alcohol use, where the findings of one trial suggest it may slightly increase student risk. Given the low certainty of the available evidence for most measures further research is required to guide efforts to facilitate the translation of evidence into practice in this setting.

Read the full abstract...

Several school-based interventions are effective in improving child diet and physical activity, and preventing excessive weight gain, and tobacco or harmful alcohol use. However, schools are frequently unsuccessful in implementing such evidence-based interventions.


1. To evaluate the benefits and harms of strategies aiming to improve school implementation of interventions to address student diet, physical activity, tobacco or alcohol use, and obesity.

2. To evaluate the benefits and harms of strategies to improve intervention implementation on measures of student diet, physical activity, obesity, tobacco use or alcohol use; describe their cost or cost-effectiveness; and any harms of strategies on schools, school staff or students.

Search strategy: 

We used standard, extensive Cochrane search methods. The latest search was between 1 September 2016 and 30 April 2021 to identify any relevant trials published since the last published review.

Selection criteria: 

We defined 'Implementation' as the use of strategies to adopt and integrate evidence-based health interventions and to change practice patterns within specific settings. We included any trial (randomised controlled trial (RCT) or non-randomised controlled trial (non-RCT)) conducted at any scale, with a parallel control group that compared a strategy to implement policies or practices to address diet, physical activity, overweight or obesity, tobacco or alcohol use by students to 'no intervention', 'usual' practice or a different implementation strategy.

Data collection and analysis: 

We used standard Cochrane methods. Given the large number of outcomes reported, we selected and included the effects of a single outcome measure for each trial for the primary (implementation) and secondary (student health behaviour and obesity) outcomes using a decision hierarchy. Where possible, we calculated standardised mean differences (SMDs) to account for variable outcome measures with 95% confidence intervals (CI). For RCTs, we conducted meta-analyses of primary and secondary outcomes using a random-effects model, or in instances where there were between two and five studies, a fixed-effect model. The synthesis of the effects for non-randomised studies followed the 'Synthesis without meta-analysis' (SWiM) guidelines.

Main results: 

We included an additional 11 trials in this update bringing the total number of included studies in the review to 38. Of these, 22 were conducted in the USA. Twenty-six studies used RCT designs. Seventeen trials tested strategies to implement healthy eating, 12 physical activity and six a combination of risk factors. Just one trial sought to increase the implementation of interventions to delay initiation or reduce the consumption of alcohol. All trials used multiple implementation strategies, the most common being educational materials, educational outreach and educational meetings.

The overall certainty of evidence was low and ranged from very low to moderate for secondary review outcomes.

Pooled analyses of RCTs found, relative to a control, the use of implementation strategies may result in a large increase in the implementation of interventions in schools (SMD 1.04, 95% CI 0.74 to 1.34; 22 RCTs, 1917 participants; low-certainty evidence). For secondary outcomes we found, relative to control, the use of implementation strategies to support intervention implementation may result in a slight improvement on measures of student diet (SMD 0.08, 95% CI 0.02 to 0.15; 11 RCTs, 16,649 participants; low-certainty evidence) and physical activity (SMD 0.09, 95% CI −0.02 to 0.19; 9 RCTs, 16,389 participants; low-certainty evidence). The effects on obesity probably suggest little to no difference (SMD −0.02, 95% CI −0.05 to 0.02; 8 RCTs, 18,618 participants; moderate-certainty evidence). The effects on tobacco use are very uncertain (SMD −0.03, 95% CIs −0.23 to 0.18; 3 RCTs, 3635 participants; very low-certainty evidence). One RCT assessed measures of student alcohol use and found strategies to support implementation may result in a slight increase in use (odds ratio 1.10, 95% CI 0.77 to 1.56; P = 0.60; 2105 participants). Few trials reported the economic evaluations of implementation strategies, the methods of which were heterogeneous and evidence graded as very uncertain. A lack of consistent terminology describing implementation strategies was an important limitation of the review.