Teaching to the Test

I really don't understand the concept of "Teaching to the Test (TTTT)." I often hear the term used in reference to No Child Left Behind. The claim is that No Child Left Behind has increased TTTT, and this is very very bad. Surely it doesn't mean teaching the material that is going to be on the test... that seems to me to be the whole point of curricula and testing. As far as I can tell, TTTT means teaching people how to answer questions on a test without really understanding the material being tested.

For a hilariously biased overview, check out the Wikipedia article on topic. Articles like this give Wikipedia a bad name, but they do provide a good laugh now and then.

It seems to me TTTT is mostly a straw man. Tests today, especially standardized tests used in public schools, are designed to test understanding. To what sort of questions could TTTT possibly apply? I can think of a few. For example, if you know how to add and multiply single-digit numbers together, then you could possibly learn and use the method for multiplying larger numbers together without really understanding what is going on. For math beyond these simple algorithms though, it gets harder for me to think of TTTT-approachable problems. Here is a practice math test put out by the Tennessee government. I don't see much TTTT-approachable material in there.

I can't think of any TTTT-approachable reading exam questions. You read a paragraph and answer questions about what you have read. How can you approach that other than by learning to read?