As a ?jung-band? conductor I realice the need for quiet and harmonic pieces that force the student to play in a very cantilena style and keep holding the long notes with lots of air support. A simple but tasteful harmonizing by Tshaikowsky also makes it a nice piece to practice intonation in the band. The level of difficulty is also not very high. Maybe a nice intermezzo in your program, just to quiet down and meditate?