Not sure if this is the best site to ask this question, but what high school subjects would generally cover mythology and creation myth? I have heard that possibly ancient history or literature in English might do, any suggestions on this? I understand that while studying a specific foreign language some mythology may be included for that specific culture, but I mean mythology from multiple cultures to potentially look at similarities and differences.
It depends. In high school, I took a Humanities course that covered Graeco-Roman and Norse mythologies. I don't know how common that type of course is, though. You'll also see some mythology covered in literature classes, such as when they cover works that have mythology in them. Finally, foreign language courses will often touch upon cultural aspects of the people who speak the language in question. Latin (and if the school is lucky enough, ancient Greek) for sure would cover mythological aspects. Maybe some teacher of Japanese somewhere covers Japanese mythology, too?
A cross-cultural study of mythology and legend would probably be a literature elective in my experience.
It may appear in history, as part of a study of a particular culture, or in a general literature class to cover things likely to be allusions, but a cross-cultural comparison would be likely a dedicated course. We had them in my high school -- one semester courses on various literary subjects, like humor, for juniors and seniors.