First off, you have to deal with that many teachers will "teach the government test" rather than teaching the whole range of issues. Government tests are often limited in their range, and only serve specific purposes.
It's been like that for years. Everything,
everything, is based on "The Test." It's one of the reasons that my mom decided to go ahead and retire last year after 32 years of teaching. Unfortunantly Bush's "no child left behind" bullcrap is only making things worse.
What's looming over our schools now is a giant, cascading failure waiting to happen. It all starts with the lower grades. There, teacher's don't have the big "test" leaning over their shoulder (though they still get a cut of the bonus when the school does well, just like the bus drivers, cafeteria workers, custodians....). For a variety of reasons - not entirely the teacher's fault - the kids come out of those grades not really knowing the basics. How to read decently, write, basic things like their multiplication tables and simple arithmetic.
So then, in 4th or 5th grade, they hit teachers like my mom who
do have to worry about "the test", but also have to deal with the fact that these kids don't know basic things that they should have learned 2-3 years earlier. It's kinda hard to teach a kid long division when he doesn't really understand 2*2=4.
But, because "the test" doesn't really test knowledge, most of the kids are still able to flub through it and pass the grade. So they go on up to middle school, not really knowing what they were taught in the early elementary grades, and in some cases
still lacking the basics.
And so the cycle continues, all the way up through high school.