School backpack searches - for or against?

I just watched the latest Brothers & Sisters episode where the Walker family debates school searches. The attorney in the family says they are legal – to the shock of others, including me. Does the 4th amendment not apply to this situation, and if not, why (hoping for law citations here, not opinions)?

Someone else says they should not be done because doing so presumes guilt. I agree with this – one of our country’s principles is “innocent until proven guilty”.

Invoking searches in schools, in my opinion, implies to young impressionable minds that they must comply to searches in general. What is a kid to think when they are forced to be searched at school, at airports… How will they know their 4th amendment rights when they are only exposed to its (controversial) exceptions?

What is your position?