Diagramming Sentences

I was watching Are you smarter than a fifth grader? 
The first grade question was as follows:   In the following sentence which word is the only word that is not part of the predicate.

Nathan threw his book at the wall.

The contestant answered threw.  Not correct.  Buzzzzzzzzz.  Threw is the predicate.  His book is part of the predicate telling what he threw and at the wall is part of the predicate telling where he threw it. 
Nathan is the answer. yeaaaaaaaa.

My question is that really a first grade question?  

I am a visual learner like over 50% of students are.  I learned the parts of a sentence by diagramming sentences.  Boring, but is it???

You could really see the relationship between the parts to the whole sentence.  I don't think they are teaching sentence construction by diagramming sentences any more. In my opinion  seeing the relationship of sentence parts without diagramming the sentence then becomes abstract learning and very difficult and hard to rememeber.

Well, in the contestant's case she flunked out of school on the first question.   Booooooo.