First, give an exit slip to your students based on a particularly important concept (PIC) for which you want to check for understanding.
Next, sort the exit slips into piles based on the method students chose to use (whether they used it perfectly or not). Choose two examples from the student work that highlight one or two probably misconceptions students still have on the chosen PIC.
Remove identifying information from the student work, photograph it (or use a document camera) and show it the next day in your class. Ask students a question about the work that requires them to think about the work. "Which one of these two examples is correct?" is not a very good question because it can be answered by guessing. "Why do I really want these two students to talk to each other about their solution?" is a good question because if students answer it, they will have to think about the concept a bit differently.
Repeat this every day.
David is a Formative Assessment Specialist for Mathematics at New Visions for Public Schools in NYC. He has been teaching since 2002, and has worked in Brooklyn, London, Bangkok, and Vancouver before moving back to the United States. He has his Masters degree in Educational Technology from UBC, and is the co-author of a mathematics textbook. He has been published in ISTE's Leading and Learning, Educational Technology Solutions, The Software Developers Journal, The Bangkok Post and Edutopia. He blogs with the Cooperative Catalyst, and is the Assessment group facilitator for Edutopia. He has also helped organize the first Edcamp in Canada, and TEDxKIDS@BC.