OMG! I would have put my foot down if they tried to do that. Even with a school honor code, that's just asking for a theft!
We've had to do this a couple of times, and they always give notice so we can opt to leave out things in the car/in our dorms. You should suggest this option to your professor because it really is distracting during an exam, especially when people leave at different times.
Yea, but the incident I described above that was just not possible (no car) and my second "final" was a computer presentation and 20 min. was not enough time to get to the apt. to pick up the laptop inbetween the finals.
I agree though, if they intend to take away your belongings you should be told WAY in advance.