Hi Tom and welcome to Tikiwiki Community!
I'm also educator, and I've been using Tiki for educational scenarios for a while (mainly at university level).
We did some complex setup for a research project a couple of years ago, using blogs for students (using the feature chibaguy poinjted out: default creation of a group for each user), and on another project, we implemented enhancements to the Wiki in order to allow the teacher to keep track of students contributions (number, size and type) on collaborative writing of wiki pages.
I hope this helps...
P.S: Off this topic, but related hint: don't try using AulaWiki Mod for the time being (even if you'll see documentation for it on edu.tw.o), set things up for your students by hand instead. At least until a new and bugfree version of Aulawiki for Tiki 2.0 is released (hopefuly in some momths)