World Health Day is a global health awareness day celebrated annually on the 7th April. The theme for 2016 was Beat Diabetes.
Here you can find a complilation of World Health Organization (WHO) infographics. WHO is a specialized agency of the United Nations that is concerned with international public health established on 7th April 1948. It could be a good idea to use them in order to promote health messages through visuals in the classroom.
More resources on WHO mediacentre.