Rex,
      I'm curious about why you are teaching appositives to seventh graders. Is it because you want to, or are you required to? There is nothing that shows that doing so is effective, and there are some good arguments that it can be harmful. (See:
http://curie.pct.edu/courses/evavra/Bib/Authors/Daiker01_SentC.htm)
There is not a lot of research on this topic, but some of the studies reviewed on that page demonstrate that teaching constructions does no good, and may be harmful, if the students are not naturally ready for them. And the evidence suggests that seventh graders are not ready for appositives (which probably naturally develop as reductions of subordinate clauses) until after they have developed subordinate clauses. And the research of Hunt, Loban, and O'Donnell has clearly demonstrated that subordinate clauses develop in grades seven through nine. Besides, there are a lot more important things to be teaching seventh graders about grammar. Hence, I'm just curious about why you are trying to teach appositives to seventh graders.

     I haven't been able to keep up with this list because, in addition to five "comp" sections, I'm teaching a new, on-line multi-cultural lit course. I have, however, started a new list dedicated exclusively to discussions of KISS grammar. I did that because of the questions I have been receiving. The list just started, and many of the current members are home schooling, but it is, of course, open to anyone in ATEG who wants to join. An explanation of the "rules" of the list is at:
http://curie.pct.edu/courses/evavra/kiss/KISSList.htm

Ed V.