Until a job can be performed remotely, I don't see how it can be taught remotely, i.e. not hands on.
I don't know anything more than what you provided in this post, but it sounds like you're talking about for-profit education centers. These are generally looked down upon and are coming under heavy scrutiny by the U.S. goverment as of lat for their false advertisements and broken promises.
It would obviously be tricky to learn plumbing without wrenches or pipes, but I don't think an onsite instructor is required.