what kind of hardware requirements should I be looking at? Should I use something on the upper end or would a lower end AMD Duron 1.2 work ok?
If this is a Public Access Production website for the entire school... Your traffic load will dictate your hardware requirement.
As far as Apache on Windows goes; Hay if you're just playing around in a lab, and want to try new things... Go ahead knock yourself out. On the other hand if you are really going to do a serious production environment server deployment...For the love of god don't even think about it.
Two Words: Administrative Overhead.
Meaning: Pick a Platform, and stick with it.
You want Windows? Then you're using IIS.
You want Apache? Then you're using some type of Unix/Linux box.
You go half and half, and you get stuck in the middle with a broken server any time anything goes wrong because the finger pointing abounds as side A is cock-sure it's side Bs fault. Security updates have to be gleaned from both sources = Time, Time, Extra steps, and A -vs- B x2 when an update hoses the box because not everybody was up-to-speed on exactly what was about to happen.
Unless you dedicated IT Staff has a lot of free time ... Stay with a commercial host. Hang together a non-critical internal access only box in a lab for testing crazy things that just popped into someone's head, and consider yourself lucky to have dodged a bullet.
Hint: I admin a production web-server (among other things) with multiple internal & external sites for our company...I'm not guessing.