I live across the street from a school. I'd walk my kid in through a side door, the only one that was unlocked, early in the morning. I asked if the front door could be opened at that hour- nope, for "security reasons" they could only have one door open (oddly, that door was completely unobserved, while the front door had cameras, and was next to the main office).
Even though I live literally next door and standing in my yard, I can see kids playing, I am exceptionally cautious. In particular, I introduced myself to the staff (they park in front of my house every day) so they knew who I was, smiled and made direct eye contact, and acted in a non-aggressive way. This greatly improved my ability to move about my yard without suspicion. They never did unlock the front gate, though. Security through theatre.
I live immediately next door to a school (~6 foot sub-street walkway between my building and the school building).
I've lived here for >25 years and am often outside my building smoking cigarettes(!). The "play area" for the kids is on the other side of my (and one other, total ~100 feet distance) building and classes are brought in and out most of the day.
No one has ever even looked at me (AFAIK) as a potential threat, and no one (school staff, parents or police) has ever asked me to "move along," or wanted to know why I was hanging around next to a school.
And living in NYC, it's not like folks will recognize me as one of the people who live in one of the 20 apartments in my building either.
In fact, I've only had positive interactions with school-related adults despite the "suspicious" behavior I display as an adult male "hanging around" an elementary/middle school "watching" the kids.
I can't say whether my experience is more common than that of TFA's author.
I do note that many parents (not that it's a bad thing necessarily) drop off/pick up their kids at school (this is NYC, so mostly not in cars, but to walk them home/wherever they need to go) at ages (8+) when I (and most of my classmates) walked to/from school (my elementary school and and this one are less than a mile apart, but 40+ years distance in time) all by ourselves with no issues.
In fact, we'd usually just go straight out to the park and play until dark, then go home.
Back then (mid-late 1970s), NYC was much more dangerous too.
As such, it seems to me that these changes are less about "keeping kids safe" and more about "security theater" to appease helicopter parents.
I could be wrong, but it seems like that's the most likely driver.
Even though I live literally next door and standing in my yard, I can see kids playing, I am exceptionally cautious. In particular, I introduced myself to the staff (they park in front of my house every day) so they knew who I was, smiled and made direct eye contact, and acted in a non-aggressive way. This greatly improved my ability to move about my yard without suspicion. They never did unlock the front gate, though. Security through theatre.