For many students in K-8 school based dance programs, the main style of dance they will be exploring is modern dance, or creative-based dance. In my teaching position, I teach 200 students a year in grades 5th-8th grade. My classes are primarily modern dance, with some exploration of hip hop and culturally based dance forms.
Despite being a professional modern dancer myself, it remains tricky to explain clearly to students "what is modern dance." Two books for children attempt just that, and I must say, did a fine job at it.
Modern Dance by Wendy Garofoli (copyright 2008) is a book for your school library. For students in grades 3rd-5th, this book explains in basic terms the origins of modern dance, some history, the format of a dance class, and more. The photos in the book are of teens dancing as well as several photos of professional artists.
Modern Dance by Andrew Solway (copyright 2009) is also a must for your school library. While similar to Garofoli's book, this book goes more in depth about the timeline of modern dance from the early 1900s until the present. There is content about dance outside of the United States, post-modern dance, and more. The visual structure of this book includes a wide variety of photos of professional level dance and text boxes with facts and short biographies. How can you not love a book that includes Trisha Brown, Pina Bausch, and Akram Khan? I would recommend this book for students in grades 3-6 (possibly as high as 7th grade).
Dancing Words Blog 
Leave a comment