We just finished our Little Mermaid, Jr run. We had 3 casts of this show - the Little Fish were K-5th - the Middle Fish were 4th-8th - and the Big Fish were 7th-12th Graders. Having done pretty much a case study of LMJr., I would say it fits best for 5th-10th as written. My K-5th group enjoyed themselves immensely and loved the music. We had some pretty respectable 2-part singing in "Kiss The Girl" and "She's In Love", but the complex harmonies were beyond that age group. Unison was perfect in most instances and totally served the story. In retrospect, I'm so glad that my little ones had the opportunity to present LMJr. I had a 7 year old Sebastian with comic timing to beat the band, and an 8-year old "Chef Louis" who brought the house down every night. With the oldest group, I missed "Sweet Child" and "The World Above". But, the Broadway Jr. version, is not the Broadway version, after all. To add all the material would have ship wrecked the 70 playtime - which is perfect for this age group - in our world. You are right about the piano vocal score - whew - not easy. I ended up playing parts in small group vocal rehearsals and leaving the accompaniment to the CD. SImilar to Millie, Jr. in that way - tough score! Also, totally worth the investment in the challenge for the kids. I LOVED the Little Mermaid, Jr. and so did all of my fish - big and small.