I agree, stay near the school. This way, you fold all of your travel in one shot (ie you fly in, take a taxi to the hotel. Done with travel, walk/quick taxi to the school). Then, when you're done, your trip to the airport/flight out/trip from airport is one fell swoop.
This depends also on the proximity of the school to the airport and surrounding hotels.
And the above comments from fenix are correct...airport hotels charge up the ass (usually), but so do ones in "downtown" of most metropolitan cities.
So, in summary, no single answer, but I've always been a fan of the failsafe that should i wake up late for my interview, I can literally RUN to the campus within 5-10 minutes vs. having to deal with transport.