No child left behind was a stupid law from W and Teddy. Some kids SHOULD be left behind.
As for teachers giving answers, I doubt many of the teachers could have scored very high on the tests themselves. So how the hell would they know the answers?
The correct answers to all questions on a given taught subject in public schools is listed in an index in the back of the Teacher's Version of all textbooks.
The direction in which to teach the curriculum is spelled out in each chapter as well, along with the questions the teacher should ask and the direction to prod the students.