Which of the following activities is an example of secondary prevention in a school setting?

Secondary prevention focuses on early detection and prompt intervention to prevent the progression of diseases or health issues. In a school setting, performing vision screenings exemplifies this approach as it aims to identify vision problems at an early stage. By screening students, potential issues can be detected and treated before they lead to more significant problems, such as learning difficulties or impaired social interactions.

The other activities listed represent different aspects of health promotion and prevention: educating about heart health and teaching nutrition classes fall under health education and primary prevention, aimed at promoting overall health and preventing issues before they arise. Administering immunizations is also classified as primary prevention, as it involves protecting individuals from infectious diseases before they occur. Therefore, vision screenings distinctly align with the principles of secondary prevention by focusing on early detection and timely intervention.