You can order a box of books from this site. They will range from toddler to young adult books. Each box contains approximately 55 lbs (give or take). You can also order more age/grade specific books, but it costs a bit more.
Call-and-response is a time-tested technique for getting attention, not just in classrooms but in the military, in churches, at sports events, and in traditional cultures in various parts of the world. Not to mention the kids love ❤ it.