It depends on how interested the school is in you. If they are really interested, telling them of other interviews provides the possibility of you going somewhere else if they wait around too long for a decision. It also lets them know that something about you is good since other schools are interested.
However, if you're a marginal or "whatever" interviewee, they may not consider you as much if they know yuo have other possibilities.
It would also depend upon how interested YOU are in THEM.
That's my opinion.