I echo somebody else's comment above that comparing this to a school board is disingenuous. A court order is far different than a school board going fishing.
For this case, a court order for information from a person's web account should have a way to subpoena the information necessary without requiring disclosure of passwords. That's reasonable, just like how with a court order a suspect must provide the keys and/or open up a safe on their property if such is specified in a search warrant. It's similar. The problem comes that with some models of computer security, that information is not available without a privacy violation (giving up a password). It's quite a conundrum.
That being said, in this case (and many others) I'm shocked that Facebook (& friends) don't have some type of "legal request mechanism" that would work as a "backdoor" for this type of thing. They can reset passwords and such, so it's hard to believe they don't have a mechanism to handle requests from legal systems for a history of posts, images, etc. The law should always require a warrant to access it if it's not publicly posted, but other than that, I'm surprised it isn't already there.