I was recently re-reading many of the postings going back about 3 months. Some of the postings, including 1 or 2 of my own, comment on limited literacy of students--either now or in decades past.
An interesting perspective on this can be obtained by looking at books intended for training teachers of shorthand. A typical high school student is/was mid-teens and has had limited experience with the affairs of life or the parlance of business. The background of teens in years past was even more variable than now, so texts had to familiarize students with words that are routine to adults or with standard spelling and punctuation.
Mr Leslie wrote a number of books on this topic, and I have others in my basement!