In the five decades between 1945 and 1996, over 2,000 nuclear tests were carried out all over the world. The International Day Against Nuclear Tests aims to raise public awareness about the effects of global nuclear weapon tests, and advocates the banning of nuclear tests as a step to achieving a safer world.
The UN's International Day Against Nuclear Tests web pages provide lots of background information on the history of nuclear tests, and the various treaties and actions that have been taken to reduce nuclear weapons and ban testing. This includes video clips and other multimedia resources.
Other resources that can support you in getting students to discuss this issue in class include: the free UN Matters Teaching Pack from UNESCO Associated Schools and five resources from the Campaign for Nuclear Disarmament. Japanese artist Isao Hashimoto has created this rather chilling time-lapse map of the 2,053 nuclear explosions which took place between 1945 and 1998.
It is quite long (nearly 15 minutes) but perhaps you could have it showing as your class comes in, to get a discussion going. (If YouTube is not allowed in your school, use this SafeShare link: http://safeshare.tv/w/fpCpuaVDWG.) https://youtu.be/LLCF7vPanrY