I don't understand the problem with "teaching to" these comprehensive tests. The tests test their knowledge of content. Kids who don't know the subject matter will do poorly; those who do will do well. Isn't that what teaching is all about?
The problem that I see with attaching merit pay to the test results is that you have to be able to follow the kids on a multi-year basis in order to determine if the teacher made a positive contribution to a child's knowledge base. If Johnnie made a 56 last year, and under Ms. Smith's tutelage made an 82 this year, then apparently, Ms. Smith deserves a merit raise. So you would have to track all of her students' progress for this year over the last (or last several).I think the "teaching to the test problem" is really a red herring.
All I can tell you is what my daughters friends tell me. Their teachers basically hand them informational packets, kind of like SAT prep packets and just do those for weeks and months at a time.