Maybe since they walk this way at least once a day, they know when there will be that big puddle. Say if it had recently rained heavily?

I think Splunge has it. I used to walk to school every day - heck, actually I still walk to the train station every day - and over time you just notice where the trouble spots are and work out a way to avoid them.

This winter the sidewalks were so icy that for a portion of my route home, I would just step off into the street and walk up the middle of the street (not a busy one, fortunately). I just noticed, like, last week that I was still doing that even though the ice is long gone. It's safe to go back to the sidewalk now.

But yes, there's a lot to be said for a regular walk on the same route through the different seasons. You notice all these little things, plants coming up in gardens, funny cracks on the sidewalk, people who walk their dogs at the same time, when houses go up for sale or get bought or get painted, and even stuff like "oh yeah, that big puddle is going to be there today at the bottom of the street because it rained all night last night."

Good guess, Splunge, but nope. Rains all the time (I'm in Portland) and this was an enormous puddle was due to a blocked drain. Not foreseeable.

And the striking thing is that the kids never walk on the opposite side of the road. Ever.

I can already picture the headline for the NYT Lifestyle section feature article:
Hot New Teen Trend: Is Dowsing the New Sexting?

Flocking. Emergent behavior. They walk on the side of the road that the kids in front of them walk on. Only the first couple of kids needed to actually encounter the puddle. They then text or call the next kids, who start off on the right side of the road. All the other kids are just following a block or two behind. They don't even know why, themselves. Like birds.

Stepford Cuckoos

Vampires. You are in the Pacific Northwest.

Atom Eyes, I just snorted water through my nose. Thanks.

They must have seen it do that before. There's a corner on my street that always gets backed up when it rains. I know where to step to avoid getting in it- and also to stand way back when traffic is moving to avoid getting splashed.

atom eyes: SNARF

Hee hee, Atom Eyes!

Nope, Teeps. I've been walking past there every day for the last four months, in the rain. Never happened.

I think IRFH has nailed it. It occurred to me, but I just thought it was too many people following blindly the person in front of them.

So strange.