University of Cambridge
University of Cambridge: Nrich: Got It
Sharpen your logical thinking and see if you can figure out the strategy to get to the target number before the computer.
Yale University
Detective Fiction: Focus on Critical Thinking
Through the use of reading crime fiction, this lesson plan helps to refine critical thinking skills and problem solving strategies which are important for the development of 21st century skills.
Other
Kids Philosophy Slam
Every year a kid-friendly philosophical question is asked and students are encouraged to submit original writing, drawing, painting, or poetry that expresses their opinions on the posed topic.
Maths Challenge
Maths challenge.net: Problem Solving Database
Need some challenging problem-solving work for your students in the following areas: Discrete, Geometry, Numbers, and Code Breaking? This is the place for an enormous database of problems aimed at high school age students. They are...
Other
Teach Net: Brain Binders
Brain binders are great teacher sources for problem solving and critical thinking with geometry. Students fold sheets of paper to create solid colors on each side. Various levels are included starting with two folds through five folds.
PBS
Pbs News Hour: Current Events Lesson Plan
An interesting way for students to dissect current events in the classroom. This lesson plan has students look at bias and develop critical thinking skills in order to digest the news media.
PBS
Pbs News Hour: Responding to Quotes and Aphorisms
The objective of this lesson plan is to teach students about responding to quotes and aphorisms. This site features a lesson plan with detailed information.
Other
Wardrobe: Educator's Guide: Vocab., Comp., Etc.
This Word document offers pages of activity ideas for fostering vocabulary development, comprehension, critical thinking and creative expression based on "The Lion, the Witch and the Wardrobe."
Other
The Critical Thinking Community: Index of Articles
Listed here is a wealth of information and articles all pertaining to the idea of critical thinking. Much of the information here can be useful in understanding what critical thinking is and how to apply it to your classroom.