It's no secret that parents want their children to have the lifelong cultural and intellectual advantages that come from being bilingual. Parents spend millions of dollars every year on classes, computer programs, and toys, all of which promise to help children learn a second language. But many of their best efforts (and investments) end in disappointment.

In The Bilingual Edge, professors and parents King and Mackey wade through the hype and provide clear insights into what actually works. No matter what your language background is--whether you never passed Spanish in high...