I guess I'm of the old school....I remember opera at the Met where the voices were trained to carry over the orchestra to the last row of the balcony....WITHOUT mics!
I think it's part of the necessary training for young performers to learn how to project, and it's the director's job (or if you're lucky, the school music or drama teacher's) to teach them how to do that!
Besides, getting good, even sound quality without an expert sound tech is nearly impossible.  I've adjudicated numerous excerpts at festivals that have the mics set for different levels, some mics that just quit working in the middle of the cutting, feedback issues, and it just ruined the group's chances to advance to the next level of competition, even though the rest of the excerpt might have been of high quality.
I wouldn't mic.  If the acoustics in your venue are muddy, perhaps you can get the custodian, shop teacher and students, or parents to help you construct some sort of a sound baffle (is that the right term?)to put behind the performers to "scoop" the sound out towards the audience.  The rear curtain idea previously mentioned is a possibility too.