Yet another education post over at Maggie's. It is a subject where people believe what they believe regardless of the evidence. Because they just know. And their own childhood experience, or their grandfather's, or their second child's, is brought forward as an illustration of some universal truth.
Anecdote. It's all just anecdote and preconceived notion that must fit into some deeply-held personal need, as it is so impervious to modification.
Do the work yourself, then may it will sink in. Identify a few of the best high schools in your state according to reputation and see what their 10th grade testing scores were. Then track back six years and see what their 4th grade scores were. Repeat for the worst high schools. You will find roughly the same schools at the top and same schools at the bottom. If you can find 1st grade scores, so much the better. Multiple years in good schools doesn't add much, multiple years in bad schools doesn't subtract much. Any difference of more than a few points is usually a demographic change because of wealth - a booming community where richer people are moving in, or a failing community where all the smart money is getting out.