It would be particularly sick if the legal case for this came down to deciding whether any adults had their privacy violated. In general, US courts have not been to fond of protecting the rights of children (which makes the children arrested for child porn of themselves trend still more poignant), and so I can easily see the case coming down to deciding if adults were harmed, effectively setting a precedent that it's…
you bet your ass it's ok to spy on kids; I made em, i can spy on em (sorry kiddos). the school district on the other hand, is not allowed to venture onto my lawn, much less into my house.
They can claim that since laptops are not tracked via GPS so it is hard to know where the kids are (at home or at school). So they can just brush this off as an 'oops' or demand that all laptops have tracking chips in them. Or they can always blame the sysadmin and just say "we told him to spy only when kids are at school, but he goofed off, so we'll just fire him" basically scapegoating one person.
Now I am not defending them, as this is a completely outrageous violation of so many rights. I am just thinking of what lies they might use in court to justify this.