Fun Ipad App for Practicing Conventions

The common core states that students should spell correctly and have control over sentence structure.  This leaves many teachers wondering what this means and how do you teach that.  One app called Grading Game helps students practice skills in conventions and it's a lot of fun.  The basis of the game is that students need to find errors in a paper in order to win points or money.  When a student points out an error, the correction is made and explained in a word or two.  At first I thought that it would be easy for students to just click anywhere in the writing until they came across an error, but the app covers that as students will lose time if they are incorrect about an error.  I know I had a lot of fun playing.  The timer is only a minute so it keeps things exciting.