Don’t let high school students revise – make them start from scratch

Greetings from the NSTA conference in Chicago.  Today’s post sprung forth after I attended a session about “chickenology” – two Ohio science teachers who are also chicken farmers use the creation of a gravity-fed chicken feeder as an engineering design project.  They bring their chickens into school to test the designs.  Fantastic.  I attended the workshop alongside Abbie Mills, Woodberry’s engineering teacher, and we got to talking about the design process in the high school classroom – how the chickenologists approached design, how Abbie does, how my wife Shari the ceramics professor does… and how I do in physics class at the smallest scale.

I’ve written already about how my test correction process became optimized when I stopped showing students their original test.  They now get only a blank version of the test, with indication of the parts for which they didn’t get full credit.  They are forced to look at every problem anew, without any indication of how they first tried to solve the problem.  Sure, some students try to reconstruct what they did originally… but they realize pretty quickly that they’re on a fool’s errand.  They just start from scratch.

Why don’t I let them see they’re original answers?  “Please can I see, so I don’t make the same mistakes again?” goes the reasonable request.  But chances are, this student won’t make the same mistake again, if they start anew with a fact or equation straight off our fact sheet, especially if they first have a conversation with a friend about the correct starting point.  And then if they do screw up again, they’re ready right now! for me to show them the conceptual error they’re making.  

But more importantly… students are unhealthily wedded to their first attempt at anything.  Having their original answer in front of them changes the exercise from “solve the problem correctly” to “see if I can explain why I was right, or at least partly right.”  Interestingly, Abbie and Shari independently have come to a similar conclusion about larger-scale design processes.  And both of them were high-level practitioners of engineering/ceramics already before they entered the classroom to teach those subjects.  They know.

Abbie holds a discussion after their first project with stick towers.  Whatever design they start with, she says, the students never, ever just tear it down and start over.  Even when their internal group discussion comes to a consensus conclusion that their design isn’t gonna work. So the post-project discussion becomes, “When did you figure out that your design wasn’t going to work?  Oh, like three class periods ago?  Why, then, did you continue to try to patch it up rather than just redesign?”  Good lesson, eh?

Yes, good meta-lesson, one that I’m glad is being taught.  Yet, I want to focus on the physics lesson at hand, not the meta-lesson.  I want to skip the whole three-day process of using hope and duct tape to finish, and instead force the student to begin anew.  For the long-term goals of my class, I want students to develop confidence in the correctness of their solutions so that they can scaffold their understanding to more and more complicated physics problems.  So I never ask students to revise anything at all.

Understand that this penchant for sticking with the first approach to a school project until death do us part is not unique to physics or engineering!  Shari faces the exact same issue with art students.  They are quite resistant to improving a project that needs more work – they want to be finished.  But if she takes the first attempt away and makes them start over, they produce an improved piece every time.  Same thing goes, she thinks, for her English teaching days: she was so, so frustrated that students “revised” an essay only by making small cosmetic changes in response to direct input from the teacher.  She thinks that had she taken the first draft completely away, made general comments, and demanded a new essay from scratch, her students’ writing would have been much improved.

As always, I’m transparent with my pedagogy.  As students bring me responses to check – lab predictions, test corrections, in-class problem solving exercises, anything – I either stamp them off as correct, or ask students to redo from scratch on a blank sheet.  The first time I place a student’s incorrect response in the garbage can, I see horrified faces: omg, that’s so harsh!  They see quickly that my calm, smiling, polite explanation of why, pedagogically, they need to start from scratch is in no way harsh.  They see that other students meet the same fate, such that my objection to their wrong physics is in no way personal.  And over the weeks they see how quickly they’re improving their physics understanding… to the point that the students themselves begin to trash partially correct responses without any intervention from me.