Adding a lesson on elementary schools is a bit too extreme imo. At least in my country, that's not really necessary. Maybe middle or senior high school might be more appropriate. The lesson might get split between economy and IT, there's no need for a full-fledged blockchain course. That should be for university and the likes of it.
No you're totally right, it's a bit extreme to put cryptocurrency in elementary curriculum. I think it should be an elective subject in college, Senior highschool isn't the right one though as that's the time that they should be focusing on finding their interest.