Britain is the only country I know of with formal certifications. There are no such set formats in the U.S. unless you elect to follow the British model. We are free to progress or flounder as we choose. I like the format of the AHS music evaluation auditions, which provide feedback and opportunity for growth without restricted repertoire. I think they should be held annually in every chapter, or the equivalent. Studio teachers with enough students should consider bringing in an outside juror on a regular basis.
In the U.S., one can obtain certification from The Harp School in Burns, Tennessee, http://www.carolmcclure.com/harpschool.html. This is given by taking appropriate exams at various levels given by adjudicators who are either themselves trained by the Associated Board of the Royal Schools of Music, or judges traveling directly from Britain, as noted by Saul, above, to many countries around the world. Anyone can request syllabi containing lists of music choices for the various levels, for harp,