Since I started publishing, I have visited with literally hundreds of classes, from kindergarten through 8th grade.
What I Do
Generally, I start by telling the students how I began. Despite being an avid reader as a kid, I graduated college wanting to write musicals, but switched to books after re-reading childhood favorite, Charlie and Chocolate Factory. After that, I read from one of my own books and talk about the writing process. Years ago, I made a series of overhead projection slides out of the drafts of my first book, The Worldwide Dessert Contest, which allows me to show students in step by step detail how the ideas behind it evolved. (They can also see my horrible handwriting).
On recent visits, I have read the opening pages of the novel "13" (co-authored with Jason Robert Brown), then played a CD of the opening song from the musical, talking about how the show evolved and made it to Broadway while allowing students to see how the same story is told in different forms.
Other topics of interest include my writing for TV (notably Cyberchase, currently on PBS), the difference between writing for children, young adults, and grown-ups, and questions about the process of publishing a book.
Of course, students usually ask lots of questions and I'm happy to make myself available for signings.
If you're interested in having me visit your school, please get in touch. Reasonable rates!