iTooch is a free app that has "more than 18,000 excercises" based off of the National Common Core Standards. Covering Math, ELA, and Science, students will get practice in all areas that state testing covers. There are different apps for Elementary, Middle School, and even a few specialty apps for English Second Language Students, and SAT practice!

Free to users, and downloadable on most any device, this app is very useful in a teachers toolbox. The state standard areas are divided by grade level and include a learn, practice, and test fucntion.Students are able to "create a user" to keep up with their scores if sharing the same device with multiple students such as multiple classes and a students each using a device in each class. Tests and Study Sessions are short but insightful helping keep the student focused. The bright colors, easy to use functions, and continuous encouragement from a function within the app that are sure to not bore your students.

http://www.edupad.com/itooch/elementary-school-app/