I never experienced any anxiety from exams or performing well in the elementary school. School was easy for me and also, coming from one of the Nordic welfare countries, I never thought that my life would somehow be ruined if I didn't do well in school. I felt much more anxiety about other kids in school since I was quite nerdy and didn't fit in well.
Consequently, I never have dreams about exams. However, I do have dreams that I have to go back to school as an adult for some reason (usually because I missed some classes or exams or something and I have to do them now). The dreams are also never about the actual classrooms but just hanging around in the school with the teenagers and feeling weird about it.