One afternoon, Lori Anderson and her 7-year-old, Lindsey, spotted a small maple tree in La Mirada, California. Anderson asked her daughter how many leaves she thought were on the tree. Lindsey’s guess? “Probably a million.”

Lindsey can grasp the concept of large numbers, and she knows that a million is a lot of leaves. She doesn’t yet have the tools to make a true estimation on her own, but scientists say this is a crucial skill for children to learn.

Estimation is more than just a guess—it’s a conclusion that comes from a methodical thought process using data and facts. “We don’t just look at something and estimate. We discuss with other people how to approach it or how to look at proportions,”