To launch my photosynthesis unit I gave students an illustration of a chloroplast with different molecule entering and exiting the organelle. I have students work in groups to solve the puzzle without me giving any answers.
CONNECT - I have used this strategy in the past because I know that collaboration is a good way to active a groups's combined schema. Most students are engaged, too, by the challenge of trying to solve a puzzle together. I know, too, that a class discussion is an important step in the process. I also know the importance of informally assessing each student's level of understanding by having students do a quick write in their notebooks
EXTEND - Over the years that I have used this lesson I have extending my thinking from have students do this alone from working collaboratively. I have also made the lesson more engaging about making a group competition to see who can solve the puzzle first. I have also incorporated the individual writing piece into a n informal assessment rather than ending with the class discussion.
CHALLENGE - A challenge that I am often confronted with is some students know right away what is going on. It often spoils for other students in the group. I like to give this to students before I even give a pretest because I don't want them to infer that it is photosynthesis from the pretest alone. I suppose that I could mention before we do this lesson that if they already know, that I could have them complete it on their own at a separate table.