In what areas do you think OmniFocus lacks the requisite flexibility? Is going to school not a large collection of tasks which have to be tracked and completed? That's pretty much the target for OmniFocus, I think :-)
A few threads I recall about classwork and OmniFocus:
http://forums.omnigroup.com/showthread.php?t=13111
http://forums.omnigroup.com/showthread.php?t=14192
http://forums.omnigroup.com/showthread.php?t=12816