Scribd is a great paid app. You pay for a subscription through the App store. It houses a great library of books for everyone. It can include new releases as well as classics of all genres. It also has audiobooks. It is a great deal becuase it provides with unlimitted access to their entire library!
Audible: Auduble is an audiobook service that allows you to pay a subscription fee and buy an audiobook once a month. It has access to new releases as well as classics.
News: The News app that comes on the Iphone is a great place for students to start getting accustomed to news articles. You can tailor the news to what they are interested in and put controls on it if need be.
Librivox: Librivox is an audiobook app that allows you access to books in the public domain (books whos author's have passed and therefore the audiobook is free).
Good Reads: Good reads is a great place to get book suggestions. They have lists of books that might be in a genre or for a specific age group. Parents can read reviews before their children read the book and students can find books similar to those that they've read.
Hoopla: Hoopla is a great free app that gives you access to audiobooks, ebooks, movies, media, tv shows, and music through your library card.
Over Drive: Over Drive is like Hoopla, it gives you access to audiobooks and ebooks through your public library card.
Epic: Epic gives you access to so many free books and they're all leveled so you can see which reading level would work best for your child.
Word Hippo: Avoid overused words and phrases in your writing with this app, which provides synonyms and antonyms in a flash.
Grammar Smash: This no-frills app is excellent for older learners, especially ESL students. Review grammar guides and lessons, then play games to practice your skills
Mad Libs: Everything you love about Mad Libs, in an app! Prompts ask you to fill in parts of speech to create a funny new story each time. The free edition comes with 21 stories.
Reading Comprehension Prep: Practice your reading comprehension and prepare for standardized tests with this app. It provides fiction and non-fiction reading passages with comprehension questions for each. The free version offers 12 stories to start with, with a new one available each week.
Spelling Bee: For ages 9-11, there are a ton of spelling activities on here with games and tests.