L.+Open+it+up+(some+of+it+anyway)

One of the great things about a wiki in the classroom is that you can keep some of it locked up and open some of it for your students. For a basic free wiki with Wikispaces, you need only choose the pages you want to open up with students, unlock them, and invite the students you want to work in them.

There are paid options within Wikispaces for further customization, but generally, the free option can work very well in a classroom.