I found this book really interesting, I would recommend to read it! (Here is a little summarize about the book and the amazon link, just in case you are interested on it)
Einstein Never Used Flashcards: How Our Children Really Learn – and Why They Need to Play More and Memorize Less by Kathy Hirsh-Pasek, Ph.D. & Roberta Michnick Golinkoff, Ph.D.
Parents, before you put your child into preschool, READ THIS BOOK. The research overwhelmingly shows the difference in how play is essential for child development in math, reading, verbal communication, science, self-awareness and social skills. NOT academics. It's very compelling.