Science Project Concrete operational 12-year-olds, like the girls shown here in a Toronto-area school, can be logical about anything they see, hear, or touch. Their science experiment—figuring out how to carry construction materials from the ground to the roof of the school—involves building elevators from Popsicle sticks, straws, tape, glue, and wood. As they work together to solve this problem, the girls discover what works and what doesn’t, document why, and make changes as a result of their discoveries.

PETER POWER/TORONTO STAR VIA GETTY IMAGES