Currently, I am studying in secondary school in the Netherlands. I am in my 5th year and we are currently covering Einstein and his theory of relativity. As people who have covered this likely know, this can get pretty confusing and difficult at times. It would be great if there was more material on the site which covers relativity. I'm not 100% sure if American AP Physics covers relativity, but I'm sure that people would benefit from it if it is covered.