When my students grow too dependent on their calculators, I ask them to find a number that, when multiplied by itself, gives them 2. Students quickly see that since 1² = 1 and 2² = 4, the answer has ...

Two students in Danielle Adler’s kindergarten class at Marcus Hook Elementary School in Marcus Hook, Pa., prepare for an addition problem. Credit: Holly Korbey for The Hechinger Report The Hechinger ...