Suburbs are not densely packed. Picking up kids in a school bus would require over an hour, even in the small suburb that I live in. Rather, everybody either drives to school or is dropped off there: the parking lot of the high school is the same square footage as the school itself (excluding the football field).
Then you probably either (a) really live a rural area/exurb or (b) don't understand that they can operate more than one bus or (c) live in one of the areas that has had local government intentionally killing off bus service.
As to the local high school parking lot, that's not an "efficiency" thing - it's a "young people getting a taste of freedom" thing.
I live in a Bay Area suburb that is decidedly not rural.
Also, how is "doubling the school's area and vastly increasing environmental damage" not an efficiency thing? Kids the world over get by without having to rely on cars to experience freedom. If your society requires people to drive multi-thousand dollar pollution machines to experience freedom, then it's not truly free.
