For those looking to increase the cognitive load and intellectual stimulation in classrooms, I highly recommend the book Making Thinking Visible: How to Promote Engagement, Understanding, and Independence for All Learners.
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From the publisher: Making Thinking Visible is a research-based approach to teaching thinking, begun at Harvard's Project Zero, that develops students' thinking dispositions, while at the same time deepening their understanding of the topics they study. Rather than a set of fixed lessons, Visible Thinking is a varied collection of practices, including thinking routines, small sets of questions or a short sequence of steps, as well as the documentation of student thinking. Using this process thinking becomes visible as the students' different viewpoints are expressed, documented, discussed and reflected upon.