One or two of my junior-high-school English teachers—public school, California, around 1970—showed us how to diagram sentences. I don’t remember diagramming (note the spelling) being pushed hard at us, but it did help me start to understand things like clauses, modification, and parts of speech. Later, in college and graduate school, I majored in linguistics, and the transformational grammar popular at the time went whole-hog with a very different system for analyzing the structure of sentences. Although my linguistics teachers were uniformly dismissive of school-taught approaches to grammar like diagramming, in the decades since those less rigorous methods have been more useful to me when writing and editing English.