Education World offers lesson planning resources geared to elementary and middle school students.  They range from five-minute fillers and learning games to a lesson plan library archive, worksheets and a lesson of the day.

Teachers.Net features over 4,000 lesson plans and classroom ideas submitted by teachers. Browse lesson plans by subject area, grade level, or search by keyword. LearningReviews note: Although there are lots of lessons, it appears nothing new has been uploaded since 2014.

The National Science Foundation’s NSDL has a database of high quality resources and tools for K-12 teachers to support STEM education.
Most of these are Open Educational Resources (OER), that can be used without restriction. Subject areas include life science, applied science, physical science, mathematics, and education. The types of resources range from lesson plans, activities, labs and simulations to reading, textbooks and units of study.

TeachableMoment.Org provides K-12 educators with timely lesson plans and resources to encourage critical thinking on issues of the day and foster a positive classroom environment. In addition to lesson plans for social/emotional learning and current issues, there ideas for classroom activities to complement the lessons. The topics are broad, ranging from bully, civil liberties and critical thinking to labor, sports, justice, and many more.

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Explore our library of humanities lesson plans by subject, theme, and grade level. Find Art & Culture lessons on anthropology, art history, folklore, mythology, religion, and more World Language lessons on languages and the cultures of which they are a part; History & Social Studies lessons on American (including our popular AP U.S. History index) and World History, civics, government and society; and Literature & Language Arts lessons, including AP Literature offerings, on great writing and great literary works throughout the ages.