The Gregg School in Chicago (founded by Dr. Gregg) used to offer summer courses for teachers of shorthand and typing. The classes were taught by experts, such as Louis Leslie and Clyde Blanchard. This article that appeared in the May 1942 issue of the Gregg Newsletter was written by a teacher who details her experience during one summer. It is interesting reading.
As a bonus, there is a 5-minute 80 wpm Shorthand Speed Test at the end of the article. The material is counted in groups of 20 standard words, with numeric markers for each minute. Test yourself if you can write the letter from dictation in 5 minutes.