Hyphens, En Dashes, Em Dashes
Q. I am copyediting a parent resource website and this comes up a lot. How do I hyphenate “this class is for three- to four-year-olds”? Is that correct? I have seen it as: three-to-four year-olds.
A. Your first version is the right one. “Three-to-four year-olds” would mean three or four children who are a year old.