My own anecdote; 12 years of Catholic School, graduated HS in early 90s.

In my Freshman year of High School, the English teacher gave us a grammar test on the first day to see where we were. Two people passed [including me--I got one question wrong], but the bulk of the students failed.

I remember being surprised that so many of my long-time classmates could fail the test.

Consequently the teacher spent the first half of the year on grammar issues instead of other literary pursuits.