You get redundant power supplies by plugging both into the same power feed.
However, you can gain some extra redundancy by plugging each power supply into a different circuit, and reducing the common point of failure (shared power source).
Although I've got a good war story on that one too, I had a machine with redundant PSUs emit a stream of smoke from one of the PSUs. It was happily up and serving while smoking out the machine room until the operator (rather sensibly) grabbed both power leads and pulled, at which point both fire and ssh went out ...
Dual power supplies is a bit overkill. Although I remember my high school admin got a central router with dual power supply, but when you plugged both in at once (from the same source) they drew too much power on a reboot and flipped the fuse after every blackout.
If the cheapest router Cisco has with dual PSUs is a 39xx, well, I guess that's what you need.
Of course, there's an argument there that "99.999% uptime" is pretty pointless for a town library in the middle of nowhere, but that's a whole 'nother argument.
Education would not have made this requirement because unless a school has two power sources the feature of dual power supplies would have no use.
Oh is that how redundant power supplies work? You need two power sources, eh?