The Electronic Frontier Foundation has just published a Frequently Asked Questions list for student blogging. This is a document that I highly recommend that school administrators who are involved in student discipline read very carefully. The EFF is not the final arbiter of what is right and wrong of course but their FAQ is loaded with information about what various courts have decided with regards to student freedom of speech in general and Internet speech in particular.
Freedom of speech on the Internet is far from settled law of course. There are a lot of gray areas. But as a teacher, an administrator or even as a student you may want to ask yourself if you really want to be a test case. School districts that lose suits charging civil rights violations spend a lot of money in settlements. And than there are all those legal costs to think about.
We all know that students are going to push the limits of policies. That is the nature of being a student. It is the responsibility of schools to show students where the lines are and help them understand the consequences of pushing the limits. Proper education can help avoid problems caused by students pushing to hard or too far. But of course for that to happen the adults in the system need to know what is what.