Absolutely nuts. At the very least, a pair or three classmates should be riding together looking out for each other.
Apparently the writer never heard of Etan Patz.
Granted, Patz was 6, not 9, but he wasn't on a subway, either.
The fact that everyone remembers Etan now some 30 years later is testimony to the rarity of such events.
ML/NJ (Friend of the Patz family)