I often hear people ask, "which is it -- are kids overworked or underprepared?" I think it's a false dichotomy. It is absolutely possible for kids to be both overworked and underprepared, and I think it's extremely common. -FedUpMom
Beyond the ever more competitive college admissions process, there's a second reason for the unprecedented levels of stress experienced by today's high school students. This, too, is hinted at by Race to Nowhere, specifically when it addresses the pressures of preparing for the Advance Placement tests. But Race to Nowhere attributes this stress to the AP itself and leaves it at that, failing to address why AP tests might be so much more stress-provoking than they were a generation ago.
To answer this question, one shouldn't look forward towards the college admissions process, but backwards towards K8 education. Here, all those watered-down math and science classes and content-impoverished social studies classes disadvantage even our top students, such that by the time they reach high school it's hard--and extremely stressful--for them to make up for lost time, whether in math, biology, chemistry, or history.
Ironically, by blaming high schools and colleges rather than elementary schools and middle schools we may end up deciding to dumb down the high school curriculum and the AP tests, rather than redesigning our K8 classes so that they actually prepare students for high school level work, and those who are potentially capable of them for AP-level classes.
But in a society that touts slowing down, de-stressing, avoiding frustration, and boosting self-esteem, and that finds it so loathsome to target instruction towards those who are most academically capable, this is not likely to happen any time soon.