Khan Academy is famous for their website, but their app makes it easy to study offline and on the go. The app can be used to review material that students don’t understand in class.

Students can watch thousands of videos which thoroughly explain topics ranging from Chemistry and Calculus to Economics and American History. For each topic, there are corresponding practice problems and questions which can be a great tool to review before a quiz or test.

With a free account, students can track progress, gaining badges as they master skills and start studying new topics. Account users can utilize the bookmark feature which allows students to continue studying while offline.

Khan Academy also has SAT prep and videos describing the college application process all the way from extracurriculars to how to write an application essay. Khan Academy is constantly adding new videos and topics for all different grade levels.  

Best of all, Khan Academy is totally free and gives students the opportunity to gain a better understanding of topics they are learning in school or explore new subjects.