It is illegal but so far nobody wants to raise an issue with it because it's a school that has a lot of govt officials, diplomats, expats, and businessmen sending their kids there. No one wants to risk stinking their own reputation by raising an issue.
As for "how", apparently if someone accidentally snaps a picture of those kids riding things they shouldn't be, anytime, and a school disciplinary officer sees it, anywhere, he can give out the warning. Has done so a few times actually.
The rationale of the rule is that vehicle operation is something not befitting the image of a student, especially a student at this (supposedly) prestigious school.
Suffice to say the damn rule made me apprehensive of riding in a friend's car for a while, and of the idea of getting my own license when I became of age.
When I decided to ask the school about the apprppriateness and legality of the rule (as an alumnus), they said "we are disappointed in you. You were a great student. We did not expect you to become someone who tries to force us to change our ways of life." That said, unless you grow up to become a nationalist or a right-winger, you are a disappointment to them, so maybe even without this vehicle use thing I'm still a disppointment to them anyway.
This story sounds absurd but yes it is supposed to be this absurd.
I still pass by this school many times as it's on my way to work. I wish I could tell those kids and new parents who might not be aware of "the system" something they should know ...
As the rule is blanket, you can ride one maybe in your school uniform but on a Saturday (maybe after you're done with cram school -- some crams ask you to wear your uniform because it's how they improve their reputation by recording live sessions with students from many good schools). If that happens and the disciplinary officer knows, you're given a strike.
How the fuck would a blanket ban of VEHICLES be a great idea?? Follow up: which culture do you live in that apparently hates transport and also, what have you been smoking?
What's the worst that a vehicle ban could do, make you walk? What's so wrong with sacrificing convenient mobility for 0.005 square miles in exchange of even a marginally cleaner and safer environment?