We have preschools and schools that are increasingly scholastic, with kids lined up in desks and sitting still for long stretches. When I was in kindergarten (1975-- it was still pretty new back then. My sister never went to kindergarten and she's only 4 years older than I) there was no such thing as an all-day kindergarten. Kindergarten was more like a typical preschool is today.
Time out of school meant time away from schoolish things. Most of us back in the day had no other lessons (maybe music, the rare few had gymnastics or other lessons). We also had no homework. I mean, zero, nada (I received my first homework in 5th grade--one page of math). Going home meant going to play. The only routine that might have changed from summer to school was an earlier bedtime (the sky wasn't light until 10pm anyway.)
We have kids who get dropped off or bussed to school, even when the school is a few blocks away. I don't see or hear kids running or biking around the neighborhoods much anymore. Even if they have run-around time at school, they are still missing before and after. (I will say this-- when I was a kid, we walked ourselves to school--even long distances. Kids were running and biking and shouting and skateboarding all over the place. Now if I see kids walking to school, they are walking calmly and quietly with their parents. Then, repeat that on the way home, but with double the energy because Hooray! school was out!)
We are in our cars more, in part because of what I mentioned-- less walking to and from school, more commuting to various lessons.
We have video games marketed to ever-younger kids. TVs are getting huge, and even if kids are not directly watching it, studies have shown having it on can still be disruptive to children.
And, yes, certainly, who knows what is in their foods anymore? Or the air? Or sprayed on our couches? Increasing use of the "air waves" for wireless devices. ????
Certain "boyish" behaviors are not tolerated, because when taken to the extreme they can be dangerous and we live in an age of zero tolerance. We've swung the pendulum pretty far the other direction, and I think that leaves kids without certain outlets-- throwing things, play-fighting with sticks, wrestling-- that could be perfectly acceptable if it weren't for our sensitivity about injury and bullying (and I'm not suggesting we shouldn't be sensitive about those things-- that's the difficulty of this particular situation).
We also have more drugs to treat this condition, and parents seem more likely to seek professional help. We are not shy anymore about talking about these kinds of things. Those drugs were out there when I was a kid-- I remember that my friend's little sister was on drugs for "hyperactivity"-- and who knows how many kids took them I didn't know about?
It does feel like there is a "war on boys" going on, even to this mom of 2 girls. But I think it is more that we have less tolerance for exuberance than we used to, and we are providing fewer and fewer outlets for that. I also like to point out that girls are not necessarily on board with these changes, either. They might comply with things more easily, they might prefer talking about things more than boys (as a whole), but I don't think they love the sitting down, I don't think they wouldn't love to have learning be more active and hands-on and, yes, exuberant. I don't think they love the seemingly endless shuttling-off to activities. I think that boys simply resist more--and are less capable of controlling their impulses than girls their age. And, of course, while girls love to run and jump, boys on the whole do seem all about running and jumping. So, I think these changes are only favoring girls because girls are capable of complying, not because this is what they prefer.