"Korean Lab" is a great, great, great Web site that provides Korean Language (국어) textbook content for Korean students in the first grade of elementary school through high school. Of course, non-native Korean language learners can use the site, as well.
I have added Korean Lab to my "Links" section, so just click on the link to go to the site and then choose either 초등학교 (Elementary School), 중학교 (Middle School), or 고등학교 (High School) from the menu. Next, choose the textbook for the Year and Semester you want to begin with. After that, choose the story you want to read. The first and second grade textbooks have audio that reads the stories for you. When you finish a page, click 다음페이지 to move to the "next page" of the story. It is a great resource.
I think I will start with grade one in elementary school and work my way up.