This concerns me. I see real possibilities for this to be more traumatizing than people imagine, for at least some children. The issue is the lack of control. IF a child only participated with their OWN consent (THEY decide for themselves, freely--not the parents or teachers deciding for them) then there is less chance for the experiment to leave lasting scars.
The thing is, if the child is forced to participate, it doesn't matter if the experiment is only for a day. The child has learned that it's possible for the people they depend on to force them to do things that are painful and traumatizing. They have discovered how vulnerable they are, and they could come away with a sense of helplessness. For some children this could have a deeper and more lasting effect than for others.
It reminds me of some of the issues that arise when torture victims process their experience. It's the combination of helplessness, pain, and willful mistreatment by others, that does the damage. The torture does not have to go on for a long time to have effects that can last a lifetime.