Encourage curiosity
Curiosity is an important component of intellectual humility. It is characterized by a proclivity to consider how something else could be, could have happened, etc. Presenting kids with an image like the one below and asking them to name all the things each one could be are two tactics for developing curiosity.
A comparable activity involves taking an object, such as a ruler, paper clip, or pen, and asking how many different things it may be. Doing either or all of these on a frequent basis helps pupils break the habit of believing that a single answer or explanation is the only, or even the best, solution.