I went to a boys grammar school where you its seemed you needed 3 things to qualify as a teacher:-

1. A degree from Oxford or Cambridge
2. Some kind of speech impediment which rendered the lessons all but incomprehensible.
3. To be somewhat round the twist.

There were two music teachers both deaf.

One or two really good exceptions however and, on recollection and by way of excusing things a bit, most of them had probably had a hard time of it during the war.