/etc/X11/xorg.conf

So, the teacher workstations were booting up to 640x400 resolution.

We had this problem last year, and we knew it's related to the teacher workstations being connected to a really long vga cable to the ceiling-mounted LCD projectors.

I figured out how to convince X.org to stop trying to be so helpful (It was probing the cable, noticing the loss of signal from the really long cable, and choosing an appropriate resolution based on that information).

I give you a chunk of /etc/X11/xorg.conf:

Section "Monitor"
    Identifier    "DELL 1505FP"
    Option        "DPMS"
    HorizSynch    30-61
    VertRefresh   56-76
EndSection

Notice the bolded entries, they keep X.org from autodetecting those settings and thus fixes the issue we had...I'm sure you don't care, but I was enlightened. It only took me a little less than a year to figure it out.