While drug tests are troublesome, at least they (hopefully) are specific and accurate and objective. Drugs are illegal and dangerous and kids shouldn't be doing them. However, I don't like drug sniffing dogs in parking lots.
I wasn't asking about the legality of such searches, but rather the public need and justification for schools to probe into a student's private life and student owned things. I fail to see how those warrantless searches help the public safety except in the most extreme circumstances.
I also find it objectionable because it leads into the areas of thought crime and guilt by association. It's one thing if I'm seen passing large amounts of cash with a known drug dealer, but something else entirely if I merely happen to have his phone number.
I also strongly object to schools looking at a student's personal notebooks; again, that becomes risk of a thought crime and violating private property and private space.