In math class, elementary school teachers appear to rely heavily on memorized algorithms and lightly on the concepts behind them. The textbooks are generally no better. This is, I believe, a huge reason for why so many American students do so poorly with algebra. Primary-level teachers need to understand high school mathematics so that they can ensure that their students understand foundational ideas that are critically important in future math classes. When the kids just memorize a bunch of algorithms, how can they start applying concepts in algebra class?
Answer: most of them can't. And can someone who managed even an average or slightly higher than average SAT math or reading score honestly be able to be]teach the finer points of high school math or literature? Answer: it's unlikely.
Your answer actually hits a major frustration that a lot of people I know have the teaching establishment: low expectations. If we lower our expectations for educators, why should we be surprised when the educational establishment advocates lowering expectations for students? For example, see the
Is Algebra necessary? thread. If teacher got a professional job with SAT scores of 470, why should s/he worry about how fractions and division are related or how they'll feed into algebra and geometry? None of this was necessary to get a professional job as a teacher, right?
Nothing will change in this country's education system until we finally admit out loud that a large portion of our public teaching corps is unqualified for the job, and that this situation is
not okay. No one arguing that we need to pay our teachers more or protect them better will ever have credibility outside of edumacation circles without also admitting that 1) schools of education need to raise their standards a lot and 2) teacher pay should be based on more than just your years of experience and highest degree obtained (regardless of subject). Change this stuff in a meaningful way and I'll start shouting to pay them more, too.