Teaching to the Test

I heard this phrase in the recent debate on Georgia education. Someone explain it to me like I've never heard it before? Please?

Correct me if I'm wrong again. Schools buy books on suitable subjects. Teach the material in the book. Then, give a test about that material. How can it work any other way?

Wasn't last years educational controversy caused by using a test that didn't conform to the subject taught? Social Studies wasn't it? Where half the kids failed.

That's how it works when you don't "teach to the test," isn't it?

Or, in that glory of Southern Wisdom, tests shouldn't match teaching materials.

I bet a few teachers will confirm that textbooks come with tests already prepared. So, let's get it clear. The test has always matched the classroom materials. That's the friggen' point of the test.