@givemersspls It
is a little high, but it honestly makes a ton of sense when you keep in mind just how densely populated Tokyo is: the 23 wards alone claim a population of 9.2 million people, with the surrounding metropolis boosting that to 13 million. If you include the greater Tokyo metropolitan area (which spans 3 prefectures), that number jumps to just over 38 million as of 2016. It's not uncommon for students to commute fairly long distances to school, so it's totally believable for schools to be
that packed.
As for why he doesn't help out, uh.... Why the hell should he? Seriously, why should he? The god responsible for this clusterfuck unilaterally gave them powers and then unilaterally kidnapped them all, only missing Yato because of a minor fuckup; come a year later, Metron realizes "oh, shit, these kids I abducted may not actually be strong enough to be my pawns, but the dude I accidentally left behind is stupid powerful, time to go snag him up, as well, and fuck what he wants". Yato has absolutely
zero obligation to acquiesce to their one-sided demands, no matter how simple it'd be for him.
Lastly, Metron gave them all abilities based on their pre-existing talents (3rd page of the first chapter), meaning he likely
can't just give them the strength to match Yato's, since basically all of his strength is a result of his magic creation and super growth abilities. I mean, he literally stated in the second chapter that he created a magic that makes him stronger while he sleeps, which was seen in his list of abilities at the end of the first chapter (super reinforced sleep magic).