I think this is an inherent problem with the American university system, where the top tier is so small and so universally desired. I think Canada does it very well. Expectations to get into top Canadian schools are grade-based and their undergraduate enrolment is much larger. If you can pull a 90%+ average,you can be sure that you can go wherever you want in Canada for university. Certainly an undergraduate education at University of Toronto might be not quite as good as Harvard's, but it seems to do wonders for the mental health of Canadian children; none of my friends in Canada have even really stressed about university admissions.
For me personally, the Canadian `safety net' also helped a lot: although I am going to Harvard next year, I knew from day one that if anything didn't work out I had myriad wonderful options in Canada.