Good question. Probably some of the [s]cannon fodder[/s] other NPC refugees brought kids with them. Sadly, though, I'm not sure how many children would survive the initial disaster- even the 20% that are left alive might not have the strength, wherewithal, or life experience necessary to escape zombies getting up, cars crashing, or massive fires breaking out. They would only have blind luck to depend on. Probably a number of the children at Nathanson College are with people they had never met before Black Friday, adults whose conscience dictated helping out a child.

There's a grim thought. 

Let's multiply those six by three, so out of the fifty-four people at Nathanson College eighteen of them are children. That work for everybody?