Quizlet is a service meant to help students study for tests, quizzes, and generally understand class content through user or teacher generated lists, which quizlet then makes quizzes, flashcards, and games out of.
Quizlet is a great site for kids to study on. You can make flash cards and study them using Learn, Scatter, and Space Race. It is best used for vocabulary terms.
It is a very safe site and you have the option of making your sets private.
It is a "flashcard-based" website that has many sets of flashcards made by people around the world. It is a good website to study from and you can even make your own sets to study from. On top of the virtual flashcards there are more ways to learn (like Space Race).