Swift Playgrounds is the most visually appealing coding app available on iPad. Users solve interactive puzzles in the guided “Learn to Code” lessons to master the basics of coding, while additional challenges let users explore code and create programs that are engaging and unique. Setting this app apart from many coding apps are two things: 1) Graphics!! It looks like this app was made by Pixar studios, making coding more fun for younger learners. 2) Text script. The use of actual text script instead of blocks containing commands (blocks are still used, but text script is realistic).
Apple produces this app, and has made available a teacher guide. Click here to view, or use your iBooks app to search iTunes store for Swift Playgrounds: Learn To Code 1 & 2.
If you're looking to teach coding to grades 5-12 students (and possibly younger), forget messing around with all the posers and download Swift Playgrounds.
I personally guarantee you that no app comes close to this one in terms of quality.