Not a new series, but one that you may have overlooked is “A Young Singer’s Journey.” This three part series from Hinshaw Music is an excellent tool for classroom use or private instruction.
Each workbook guides students through basic theory and sight-reading activities, as well as direction for healthy sound production, all specifically pertaining to the needs of a singer. The accompanying audio CD, laminated keyboard and booklet of warm-up exercises give students the tools to have productive and focused practice time, even without the teacher.
Because the workbooks are of graduated difficulty (Book I, Book II, & Book III), they would be especially useful for working with students of different skill levels in the same class or lesson. A good comparison to what this series has to offer would be to liken it to the lesson method books that are readily available for piano and other instruments.
If your concentration is the young choral ensemble rather than individual singers, Stanton’s very strongly recommends “Inside the Elementary School Chorus” by Patricia Bourne. This inspiring and practical text will guide you step-by-step if you are planning to start a beginning choir, or give you new ways to build and strengthen your current elementary group. The book also includes a DVD that provides sight and sound to the strategies shared in the text.