I never paid school fees because the school paid them for me but I think if you paid the voluntary fees you got a free photocopy card (wow, lol) and you did have to pay into the library trust which was probably around $50 or something. I have no idea what that was for, but it sounds like it was new books (not that I saw many of those...)
At my brother's Primary school, if you don't pay your voluntary fees then you can't go on excursions, which is pretty lame IMO because you're essentially paying twice for excursions.
lol, droodles. You reminded me of the out of uniform days, where you're supposed to bring a "gold coin donation" but if you didn't pay up (and you were out of uniform) then you got a detention. Of course, coming out of uniform is optional in the first place, so it's probably still voluntary.