Schools are more densely packed than ever... you've got too many kids. There are also more kids coming to the same school form farther distances (more spread out) so having a fleet of buses in the AM and PM to pick all of them up/take them home is cost prohibitive for schools. And with so many extracurricular activities, some NOT at the school, it makes that more difficult nowadays to just have a bus do it all. My kids attend the same school, which has elementary, middle school, Jr/Sr high on the same campus. And they get out at different times.
It's the same argument for carpooling (which WAS a big thing decades ago), city transportation via bus or train/rail. Many more people that overwhelm a standard central transportation mechanism.
Automobiles have made the American way of life much more flexible, and inefficient at the same time.
But all that just proves that having all those individual kids being picked up by individual parents is wasteful. You can't say that ALL those kids are going to completely different places that are unreachable by school bus or walking. I've picked up friends' kids from school before, and I was just taking them to their home, which wasn't far away. The parents are responsible for deciding their kid HAS to be picked up. It's mostly privilege. If the extra-curriculars are too far away, that means they aren't school sponsored. Which means they're paying for it, AND paying extra for using their vehicle & their time to shuttle their kid around. I don't see how all these parents have the time and money for it. I was in all sorts of extra-curricular activities all through school and summer - sports year-round, music, theater, etc - I rarely had to be picked up from school. Getting picked up from school meant you had a doctor or dentist appointment, or got sick. It was rare.
I understand people keep moving further and further away from cities into suburbs because that's where they prefer to live because of housing costs, space, etc. But there's still usually schools nearby in most places. You can't tell me all these kids NEED to be picked up.
I just read some articles, one saying it's due to a shortage school bus drivers. Another gave several factors - extra-curriculars, doctor/dentist appointments, parents living farther away from the school. These aren't inevitable factors, they're CHOICES. Taxpayers and school boards deciding they don't want to pay more for bus driver salaries, parents deciding to live far from their child's school or send them to a school further away via school choice or private schooling, the choice of extra-curriculars that require traveling far from school, or simply not wanting their kids to ride the bus or walk because they're overprotective. I know things like dance classes have become a HUGE business now, which contributes to this. Not coincidentally, dance usually isn't taught in schools. What started off as small, private dance studios filling a need has become an industry, with competitive dance taking the place of sports for many families (which is why you won't see schools adding competitive dance anytime soon - the dance school industry won't let them cut into their business). These for-profit businesses targeted at school-aged children are as much to blame for the car pickups as anything else.
Okay, enough ranting. I'm just saying that it's mostly choice that got us here and people just accept it without realizing they contribute to it.