Good points lesouris. With my own t'ween daughters we've done our best to mitigate these risks.
First of all, they're not connected whatsoever, no Facebook or other social networks, no devices, our house pc is in the kitchen and they need to ask mom to unlock her tablet. I know that sounds absolutely tyrannical, but interestingly, they've shown no interest in sitting in front of screens with their pals, and instead their pals instead come over to our house. When I ask them about their lack of screen time, they're rather dismissive of kids that spend their time on social, or even worse in their minds are the boys who spend their days alone in the basement playing Mindcraft or whatnot. Instead of electronic connectivity, we've encouraged their friends to come over to our house to hang out, which gives the added benefit of knowing who their friends are - so far they've chosen great friends (positive outlooks, caring/sharing, and education/future-focused, overall kind kids).
Second of all, we've taught our daughters to think of the long game. It's not about passing the test, but about aiming your education to something you think you might enjoy. From a young age I've told them both that my only requirement is that they stay in maths and science through high school, because far too many girls drop out of these subjects and then end up pursuing useless degrees in university. I have help in this with their aunt, a well paid professional structural engineer. Not that I care what job they take on, but with math and science I feel they'll be more competitively placed for whatever job they want to do, from dance instructor to astronaut. My girls do have math and french tutors, but one on one, and designed not to add pressure, but instead how to cope and work through their daily studies. So, school stress is pretty light here. Interestingly, my girls have been very driven personally about education, but when I hear them talking, it's about the long game, not aceing some specific test.
Third, free exercise and electronic-free downtime. There's no organized sports teams in the Beez household, yet my girls are fit and trim. Instead we're out on our bicycles, walking the dog, running with their friends, or our favourite, swimming in Regent Park for hours on end. So, no competitive pressure there. When we're down, you'll often find the lot of us in the livingroom reading book, yes, real paper ones we get from the local library or our favourite trips to Chapters to peruse the young adult chapter books. Both my girls are voracious readers in English and starting to be in French.
Fourth, excellent diets. No soda, few stimulants (caffeine, sugar), white bread or sugary cereals in my house, and it's not that we ban them, the kids just don't want them, nor do we end every meal with a sugary treat. Schools have done a good job telling kids to stay away from them. Their friends look away in mock horror at my girls' favourite pizza toppings, broccoli, spinach and chicken on olive oil with thin whole wheat crust. I think we go through a ton of brussel sprouts a month, and a zoos worth of bananas. But it seems to work, as they are fit and have good concentration. Not that we don't go through a few tubs of ice cream a month in the summer months, they are kids afterall.
Lastly, focus on strong family foundations and economic stability. My wife and I chose each other carefully, did everything we could to ensure both our relationship and our economic circumstances were well founded before having kids. And our lives are about the kids, so I've worked hard to ensure I can do my part to support the family while not working long hours. Meanwhile my wife works only half time, meaning she's available more for the kids. A big part of family stability for me is one of one time, which means I go for walks with one kid, drop by Starbucks and listen about what's going on in their lives. We did have some laughs together when they started sex ed, but we're pretty open about all that stuff too, no subject is out of bounds. Eating almost every meal together at the dining room table helps too.
So, in summary, my plan to keep youth anxiety at bay is: limited connectivity replaced by physical connections, long-term focus on education plus tutors to guide not drill, free exercise as opposed to organized sports, stimulant-free mostly low-glycemic diets and most importantly providing a safe, open and strong family setting. None of this was easy, and took a lot of planning on my wife's and my part. And things could still go crazy, as we've all heard of the kids from seamingly perfect homes getting into distress, so I'm not delusional to think I've got anxiety licked, but if I can get these girls into strong women with healthy self esteem I'll know I've done my best.