If you have access to a computer and a printer, I suggest that you prepare a document yourself. I know this is not the same as a formal qualification but it will give a future employer an idea of what the person can do.
You can include the name of the charity, how many hours the person has studied, the level and a comment about their ability in some or all of the following: grammar, vocabulary, speaking, listening, reading, writing. The comment can be as simple as good, very good, excellent.
At the same time, you can continue contacting schools. It is very difficult to become an examining centre and I don't think this is the best option for you.
For ideas about testing, have you looked in the tests and exams forum on this site?
Best of luck,