Final answer:
A public health nurse should focus on interventions like handwashing, public health education, and vaccinations for promoting primary prevention to elementary school students.
Step-by-step explanation:
When presenting to third through sixth graders at an elementary school, a public health nurse focusing on primary prevention can select several effective intervention strategies to promote better health among the students. Among these, handwashing is a simple yet highly effective method to prevent the spread of many communicable diseases. Additionally, providing public health education on topics such as nutrition, exercise, and illness prevention can significantly contribute to children's understanding and adoption of healthy habits. Finally, discussing the importance of vaccinations is a key element in preventing diseases and protecting the community at large. These preventive interventions are foundational in creating sustainable health outcomes and reducing future health disparities.