At Trail Ridge Middle School, which is forty minutes north of Denver, in Longmont, the old Colorado is giving way to the new. A stuffed grizzly that once stood at the entrance has been banished to a dusky back hallway, and many of the students are the children of tech workers. On a recent weekday morning, Anna Mills, a sixth-grade science teacher, shouted from the front of the classroom, “Grab your iPads and your Spheros!” When her command didn’t work, she clapped twice, and this code was successful: her two dozen students clapped back, roughly in unison, and began getting up from their desks. Mills had divided her class into groups of three, and the leader