I was being a little facetious there. IDK when was the last time you went to a school vocal concert. I've got the holidays coming up and will be subjected to a couple in the not distant future. And then especially if they're doing this in a classroom - not the auditorium or even the gym... And ultimately, what is this for? Parents and grandparents will be tickled just to hear anything. If anybody has any expectations of a "radio-ready" production from this debacle, they should lay those down right now.
But I was also dead serious. My bloody phone does a surprisingly good job of capturing reasonably flat and natural sound even at relatively high volumes. As with anything, it's going to be all about placement anyway. The phone is portable and convenient and you've probably got a few in the classroom already. Set up as many as you want and either pick the best or mix a few together. With a little care, it'll be as good as anything else.