Apache as Proxy question

[Shaken Angel]

Hey all,

I'm involved with setting up an Apache server on a Linux box as a proxy
web server for a local school.  However, this being a *school*, meaning a
high school setup, the folks in charge don't want kids going to any of the
Internet's plethora of goat porn sites.  I see in the documentation for
Apache's proxy module that there's a ProxyBlock directive for blocking out
sites, but I don't see the logical "ProxyAllow" directive for *allowing*
sites.  See, what I/the school want to do is *block* every site on the
Internet *except* for a few, like library databases and the like, and I
don't especially relish the thought of having a ProxyBlock directive with
a billion-million URLs in it.  I'm not CyberSitter.

Is there any way to do this with Apache's Proxy module?  Any help would be
greatly appreciated!  Thankee.

-- john f., miami u library systems