This is a good site for Social Studies teachers to find US primary source documents to help supplement the material being taught. There are a lot of different sources on here.
This website has so many resources for all grades and areas of learning. They're not just broken down into math, science, and social studies. Under each subject area the resources are broken down further.
Website highlights Social Studies (Geography, United States History, World History, Economics, and Government) sites. In order to make the list, these sites have to be accessible and challenging to English Language Learners and native-speakers alike.
Founded in 1907, the Organization of American Historians (OAH) is the largest professional society dedicated to the teaching and study of American history. The mission of the organization is to promote excellence in the scholarship, teaching, and presentation of American history, and to encourage wide discussion of historical questions and equitable treatment of all practitioners of history.
This cite has complete lesson plans for various grades and subjects, but I think that Social Studies and Science will find it most helpful. There are also activities that the students can do at home or during class.
This website has links lesson plans and resources for social studies teachers who are teaching about early river civilizations. It is originally made for middle school, but could be adapted for high school.
This is a great site to find history lesson plans, which are divided by era. They also have tips on how find primary sources and how to use them in the classroom.
This is a good site for teachers to check in on and learn new things to teach. Also, it could be used to have the kids read an article and reflect on it or use for research.
This site is sponsored by Northern Illinois University and is a primary source material for one of America's most celebrated Presidents. It has text, images, videos and interactive features as well.