This is something we're constantly contacted about.
Sadly, there are no legitimate credentials like college degrees that apply directly to body piercing. One could go through training as a surgical technologist, as the curriculum would largely parallel the knowledge needed to be a competent piercer. If anything, it should go beyond the necessary background knowledge to be a piercer. However, the time invested and the corresponding salary as a surgical tech would far outweigh what the average piercer would expect.
That doesn't mean that college classes aren't appropriate at all. Taking classes in anatomy, chemistry, aseptic technique, etc. would help provide necessary building blocks for piercing safely and with intent. We need to understand how skin heals, how materials react inside the body in the short and long term, and how to reduce/prevent infections, as well as many other pieces of background knowledge. Right now, these fundamental subjects aren't available in piercing seminars or as more than a primer at our professional conference.
Once you've mastered the building blocks, to pierce well there is no substitute for hands on instruction. Some piercing seminars may provide a glimpse of these techniques, but right now there is no alternative for a structured, thorough apprenticeship/internship. This requires time and effort on the part of experienced piercers, volunteering their time to make sure those being trained truly have a mastery before they begin piercing without supervision.
Unfortunately, many of those offering paid instruction or apprenticeships are propagating misinformation and giving no more than a "monkey see, monkey do" experience. This hurts us all in the long run, since these "piercers" don't understand the "whys", cannot adapt their techniques to specific anatomies or situations, and often perform piercings that don't fit a person's body and/or lifestyle. It also gives piercing a bad name as more and more people have poor experiences getting pierced or healing their piercings.