My 11 year old son (6th grade) is having some difficulty diagramming sentences. We are using the purple book, Student Workbook 1. Is there a resource that has extra practice sentences that he can diagram? When we go through and correct them, he seems to understand but I would like to give him additional sentences to do on his own before I feel confident enough to move on. His struggle is mostly with Adverbs that tell when, where and how often. Thanks!