I've had some pressure on me from a first grade teacher to diagram sentences. Well, more like pressure to emphasis sentence diagramming. So I ask my father (an English professor) for his opinion. He said with his experience and research it would seem that with emphasis on sentence diagramming all you'll have are really good diagrammers. hahah! So true and I wish I had thought of that response.
...he suggest some links this is one of them-
http://www.thefreelibrary.com/Sentence diagramming: no unanimity among users.-a0165912653