There are two organizations that certify farriers. B.W.F.A. (Brotherhood of Working Farriers Association) is one of them. Anyone who is confident and is really serious about their shoeing ability will be certified. This offers the horse owner proof their farrier has the basic knowledge and skill to shoe or trim their horse correctly. No single horse hoof is created equal, not even on the same horse. It is a skill and art to set your horse up to travel in the most balanced, natural and correct manner possible. Taking a shoe right out of the box and nailing it to the hoof is not going to do the job correctly. A horse may even be crippled for life by improper shoeing.
I attended the Oklahoma Horseshoeing School in Purcell, OK. After successfully completing the Professional Horse Shoeing Course (consisting of 72 hours of lecture, 360 hours of horseshoeing and more lab hours than I can count) I was able to complete the course. Only then was I allowed to take the written and practical hot & cold shoeing exams under a certified licensed Master Farrier's supervision.
Although you do not have to pass the exams to receive a course Certificate of Completion (which means if you can just make it through the class you get a Certificate of Completion) you must attend a minimum 8 week course and MUST pass all certification exams just to receive your Certitied Apprentice status and license. From there you move on to Journeyman I and so on.
This is why using a Certified Farrier is so important. Anyone can open a horseshoeing school, even your grandmother. Anyone can attend a horseshoeing school. There are no guidelines or requirements. But choosing a school that will teach you what you need to know to get your certification and passing your certification tests. That's another story.
Every farrier that has actually completed a professional horse shoeing school course of study should have a document certifying completion of the course and should be able to produce such a document. Every farrier that is ALSO certified and licensed will be able to produce a card from their association showing their level of certification and licensing. Anyone can say they have attended school or are certified. Unfortunately it doesn't always mean they have or are.
You may call B.W.F.A. at (706) 397-8047 to find out if your farrier is actually certified with them, or ask you farrier to produce his card.