I studied horn playing when young and played for a short time as a freelance horn player before going into teaching. I used to teach all brass instruments and I used to teach all UK grade exam levels. I have two performance diplomas ALCM and LTCL. After the LTCL I continued to study horn playing so I know that all diplomas are well below the standard needed even for low level freelance playing.
In my early 40s I started oboe lessons. Had to give up the horn in order to concentrate on the oboe. I have studied oboe and cor anglais at a music conservatoire. I do not teach the oboe.
My oboe playing standard is better than my horn playing standard when young. I did not play the oboe as a child, although this is what I asked to play at age 11.