Here's a book that would be a great resource for you:
Teaching Student-Centered Mathematics: Developmentally Appropriate Instruction for Grades 3-5 (Volume II) (2nd Edition) (Teaching Student-Centered Mathematics Series)Mar 2, 2013
by John A. Van de Walle and Karen S. Karp
Actually, if you go on Amazon, you can get this book (just an earlier version) and the one for grades K-2 very cheaply used.