Under no circumstance does the tenant have to leave during showings. Why would they. They paid to rent the house for the entire month? Meaning they have the right to reside there the entire month, so they do not have to leave. The lockbox you are probably wrong about too, but that is more of a grey area. It's best you try to come to some amicable agreement because you are in the wrong on this one. Perhaps give them movie tickets during showings or something. I'm just thinking out loud on that one.