I checked out one of these top 10 or 20 lists and Math Guide was one of the sites listed. Math Guide has lessons, interactive quizzes, and worksheet generators.
I checked out the lesson in Pre-Algebra titled "Operations on Integers". The lesson comes with a reading assignment that includes several videos and a quiz for each section. This means they read a section, watch the video and then take the appropriate quiz.
The quiz has a few questions that can be checked at the end. If an answer is wrong, the student is given the correct answer and another chance to take a different quiz. Even if the results are 100 percent, another quiz is offered. They can also go into the quizzes without reading the lesson or watching the videos so students can easily return again and again to practice. The quiz is a simply written one which should work on the iPad without any trouble.
They cover pre-algebra, algebra, geometry, college algebra or advance algebra with vectors, trig, and conic sections. The index lists all the subjects and each lesson has a guide so you know if there is a reading, video, quiz, or activity. In addition, there are worksheet generators available for most topics.
Furthermore, there is a teacher section with additional materials to help round out the lessons. In the teacher section there are tutorials, worksheet generator, standardized test help, several general review games, research and links.
This is a very nice site with everything you need to plan units or to use as differentiation so students get the scaffolding they need. For me, I love they offer math baseball, football and jeopardy templates so teachers can design their own versions of these popular games.
The one link takes teachers to a website for integrating computer technology into the classroom. Topics include common core math, standardized test prep, math resources, software and technology integration. The technology integration looks at the topic in general, offers sites to find materials, and other information.