Look at what happened to Jesus. He gave his life teaching some really cool stuff, which boils down to unconditional love and nonviolent resistance to injustice. Then people start a church institution, and create a hierarchy of people who are authorized by their great education and expertise to interpret what Jesus said and did, and the next thing you know, you've got the Spanish Inquisition and the genocide of indigenous people around the globe, all in the name of Jesus. Mohammed – same thing. Even Mary Baker Eddy, with the care she made to create a democratic, non-hierarchical institution to protect her teaching, is effectively revered as a god by some Christian Scientists, her teaching skewed.
It seems to be pretty universal. Any time you create an institution to protect a precious teaching, a hierarchy is created to run the institution; the hierarchy separates those who have passed the written test and received the diploma from those who haven't, and the credential becomes more important than the teaching. The teaching is corrupted.
So maybe it's better to produce no institution at all, and to keep the teaching at the most accessible, equally available to all.
Besides, things like certification or ordination are based on fear – fear that the teaching will be corrupted if it is allowed to be taught by someone who hasn't had the "proper education." Yet if the teaching is true, it will always be there. It cannot be corrupted. If someone gets it wrong, it will show in their life.
When you don't have credentials, you stand on equal ground with your students. You have to prove your knowledge. If what you offer meets their needs, they will come to you.