Holy SHIT!

You notice that the center of the room has started to tremble and bulge, a fact the girls seem oblivious to. It must be the noise in there, they can't hear it... before you can think about it any more, a huge monstrosity breaks out of the soil, a thing that looks like a freakish tree monster with thick, phallic tentacles instead of branches. The girls panic and try to run for the door, but the largest, non-penis tipped tendrils lash out and blick off the doors and windows.

It is only too obvious what this monster intends to do to these girls, and the locker room is only just down the halls. So really, you have two options.