Need to know basis

One of our school's more interesting policies and one of the ones that most annoys the students is its habit of never letting us know anything more than twenty-four hours ahead of time. For example, we're going on a trip tomorrow and no one, not even the Madrichot have any idea where, until when, or what we need to bring. We got our testing schedule yesterday for our tests next week. I don't know if the policy is only motivated by their simply not knowing until the day before or if there are more sinister motives lurking here, but I have noticed that someone in the Administration usually does know what's going on and is perfectly willing to tell us when we ask them. So is there any legitimate pedagogic (oooh, big word. and probably misspelled) reason not to tell students things ahead of time or do they simply not realize the natural human urge that people have to know what's going on? I know that while flying El-Al, passengers can get a minute-to-minute flight update on the time left, height off the ground, air temperature outside, and a lot of other things that no one has to know. And I love it. I think that everyone in authority ought to tell people as much information as they can without hurting anyone and stop this nonsense fo anticipation.