If you're borrowing money to pay for a degree, going to a school where you are not at the very top of the class is really taking a big risk.
I especially cringe at the idea that Gladwell is saying it's statistically better to do something, when he has a known history of deliberately misinterpreting data and massaging numbers to get the result he wants.
While I think people should be much more accepting of 2nd- and 3rd-tier schools as options than they often are, kids should absolutely push themselves for the best-ranked school they can get into (assuming they also have a solid program for whatever field/major they're interested in). Not only is it beneficial to surround yourself with people who are smarter than you are, there are also second-order effects to attending an elite university, like making connections that can help you along with your career later. Not to mention that if a recruiter sees two recent-grad resumes that are identical except for the name of the school, they're going to pick the candidate that went to the "better" school.
Certainly you don't want to set yourself up for failure; if that elite school is going to be such a struggle that you're eventually going to be washed out, that's probably not a good outcome, and a lower-tier school would have been a better choice. But, absent that, I think it's good advice to attend the best school you can get into.
It's just more fun, and it also puts me on my best game.
edit: I agree that the first part of this comment is too harsh, see child thread
But it's more fun when the people pushing you are your friends and peers. In contrast, how many PHD researchers with a spouse and kids want to study and get coffee with a 19 year old undergrad?
Gladwell says you're only comparing against yourself against your peers at your school, and not the world, but for me, I've absolutely compared myself from people from other universities (and for that matter, other countries).
For example, there are people 2-3 years younger than me who have a public output of projects/writing that is 100 times more than mine. I'm probably somewhat high up among in my own university in project output, but I still made this comparison, partially because online communities allow me to hear about these people.