I read this short story over a decade book in a children's or young adult anthology. I only remember fuzzy details, but the gist was that the world was facing an alien invasion who were destroying/killing all humans. The aliens had the power to sense metal from long distances, so it was essentially impossible for people with braces to hide. I think -- but I might be remembering wrong -- that the main characters thought that the aliens were weak around water and that they would be safe if they made it to a lake or something similar, but they were wrong, and the shorty story didn't end well for them.
Thanks for any help anyone can provide!
