"The researchers conjecture that when children are in control of how they spend their time, they are able to get more practice working toward goals and figuring out what to do next. For instance, the researchers write, a child with a free afternoon ahead of her might decide to read a book. Once she's finished, she might decide to draw a picture about the book, and then she'll decide to show the drawing to her family. This child will learn more than another child who completes the same activities, but is given explicit instructions throughout the process....The researchers acknowledge that their study only proves correlation, but not causation"

Read all about it in EdWeek.