That's an interesting idea, but I'm specifically interested
in chroot because I need to convert some of my thin clients
(Edubuntu 8.04 LTSP) to "fat clients" a la

https://help.ubuntu.com/community/UbuntuLTSP/LTSPFatClients

and doing it from scratch looks pretty complicated. I'm
committed to Ubuntu LTSP for now, depend on it for my school,
and have been trying to focus whatever education time
I have on furthering our development goals.

The network consists of some Pentium IIs and IIIs that I
salvaged from scrap and some more powerful units that
are wasting their CPU cycles and memory capacity. In fact,
I need to be able to run some of the relatively graphics-
intensive programs, Flash etc., without their slowing down
so much as they do now.

Maybe the best way is, as you recommend, set up another
server that I can afford to have messed up beyond repair
if I make too big a mistake. Even then I need to learn
about chroot. The man instructions are so hard to
understand and I haven't found any specific steps to
create a sandbox.