In the camp I taught in, challah was made every week. Dough was made on Thursday, let rise and braided and baked on Friday. A major job for the challah person. Many groups make a diagram with the children's name and position. The challah taken and burnt is used to mark one corner so you know the tray position.
Some camps bake the challah on parchment papers with the names on the paper.
Others use popsicile sticks with the kids name in permanet marker. The stick is put on the bottom of the challah and will stick long enough to label the challah until you bag the challah. Of course each bag has to be labeled as to the childs name and group. Clay Challahs and Play Shabbat Sets. Making clay challahs out of polymer clay or homemade clay is also a great project.