What can you infer from a single incident?

Crooked Timber is talking about the Madison incident involving third grade teachers assigning their students to write letters calling for withdrawal from Iraq. It's a good discussion, even though they say this about me:

Ann Althouse, oddly, uses the case as a reason to suspect that the District does not have its act together—an odd conclusion to draw from a single instance in which it does the right thing effectively and immediately.

Here's what I said:

The project was cancelled -- school district policy prohibits teachers from presenting controversial issues with bias and promoting their personal political views.

I wonder how well that policy is enforced. That a group of five teachers thought this was an acceptable assignment suggests that it's hardly enforced at all.

"I don't see it as a controversial issue." I love that. It's so it depends on what the meaning of controversial is. Community standards seem to apply to that. And we're all here in Madison, Wisconsin.

What can you infer from a single incident? In this case, you have five teachers who got together and planned something without anyone figuring out what the problem was and one of them continuing to assert that it is not a controversial issue. How did these teachers arrive at such a mindset? From living and working in a particular environment, I would assume. Oh, but the system "does the right thing effectively and immediately," Crooked Timber says. Not really. The response only came because parents got mad. If a letter describing the assignment had not been sent to the parents, would anything have happened? What evidence do we have that the school district's policy has any mechanism of enforcement? I think the fact that the teachers thought what they were doing is fine strongly suggests that the policy is not ingrained in the practice of teaching in the district.