Is this show suitable for ages 8-14 (content/vocals)?

I really think it would be great for that age level. John and Mark created this show for middle-high school, but the two of them understand all age voicing, material and what is appropriate better than anyone I know!  Definitely get the free copy and give it a read.  I don't know tour exact situation- in school, after school program, but I would use it myself for that age.