Evidence strength

The EEF 'padlock' rating

The Toolkit presents a rating of the security of the evidence for each approach. This is illustrated on the Toolkit website using a padlock icon so it is sometimes referred to as the 'padlock' rating. This rating provides an overall estimate of the robustness of the evidence, to help support professional decision-making in schools. 

The 'padlock' rating for each strand is based on:

  • the number and types of research studies available;
  • the outcomes measured in those studies;
  • the quality of the studies and whether they enable researchers to draw conclusions about impact;
  • the consistency of the impact estimates in the different studies.

The following descriptions provide a brief description of what each padlock rating means. :

🔒 = Very limited evidence: No evidence reviews available, only individual research studies.

🔒 🔒 = Limited evidence: At least one evidence review. Reviews include studies with relevant outcomes, and studies with methods which enable researchers to draw weak conclusions about impact.

🔒 🔒 🔒 = Moderate evidence: At least two evidence reviews. Reviews include studies with relevant outcomes, and studies with methods and analysis which enable researchers to draw moderate conclusions about impact.

🔒 🔒 🔒 🔒 = Extensive evidence: At least 3 evidence reviews. Reviews include studies with highly relevant outcomes, and studies with methods and analysis which enable researchers to draw strong conclusions about impact. Impact estimates are broadly consistent across studies.

🔒 🔒 🔒 🔒 🔒 = Very Extensive evidence: At least 5 evidence reviews. Reviews are recent, and include studies with highly relevant outcomes, and studies with methods and analysis which enable researchers to draw strong conclusions about impact. Impact estimates are consistent across studies.

For more detail on how the evidence security rating is allocated see the Toolkit Manual