I meant to highlight this weeks ago, but it was right when I was going to Georgia for my grandmother's memorial service. Dan Harper wrote an excellent article and persuasive advocating progressive religious education.
He highlights the shortage of resources in the field, which prompted me to buy a book on the subject, namely Sherwood Gates's The Junior Church Manual (Doubleday, 1929). Little hints in it tell me that Unitarians and Universalists probably used it. (I got it through Alibris.com quite cheaply.)
But back to Dan Harper. Read Progressive religious education.