I was going to say training.
It could be a fear response since he doesn't know what the kids will do. They move so fast and just stick their hands out towards our pups and that can be scary. Kaji is fearful too, but he has the "flight" response instead of "fight." He'd much rather run away than have to deal with kids. From afar, he'll growl at kids to let them know he's unsure. If they get too close he runs. He's getting better with training, and because I now completely control every encounter with strangers.