I have a fifth grader in public school now, and as far as I can tell, schools are nearly incapable of identifying advanced learners, and most teachers don't have the training to teach differentiated math/science. So we settle on curriculums that target the "bottom average." The bright kids get bored and drift away, the slower kids get help, but almost never enough, and the middle group never get properly challenged.
It took two years to get my son math instruction appropriate to his level, and now the school system doesn't seem to know what to do with a 10 year-old who is finishing up Algebra 1. The answer seems to be Kahn Academy, which is not enough. I can't imagine what the battle is like for a single parent with two jobs, or parents who are not native speakers.