Sunday, July 17, 2011

Understanding by Design, Chapter 7

I'm a little behind, both in reading the chapters and in posting my thoughts about them. Part of this may be because I'm not happy with most of my assessments (which are the topic of chapter 7 & 8). Either my students find them too difficult, or they seem too trivial, too memorization-based to me.

The goal is to "convict" students of understanding specific goals or standards, using a "preponderance of evidence" from assessments that probe those goals/standards. Most traditional paper-and-pencil assessments probe simpler knowledge and skills, rather than deeper, structural understanding. Not that a student with real understanding wouldn't do well on them, but it's possible for a student who does well not to have that deep understanding, just by having memorized the surface skills. To probe for understanding, we need to see if kids can apply their understanding to at least marginally new situations. In my classes, this usually results in students complaining (during the test) "You didn't teach us this stuff!" as if they were monkeys trained to jump through a thin blue hoop and completely baffled by being asked to jump through wide red hoop. Getting students past this is a major goal for the upcoming year...

Before I can get there, I need to plan the evidence I'm going to collect. Let me start with the difference between velocity and acceleration (a major stumbling block for many students). What would provide evidence that a student understands the differences?
  • Choose correct formula for a situation
  • Correctly label a situation (verbal description, video, graph) as constant velocity or changing velocity/acceleration
  • Solve traditional problems
  • Sketch graphs for constant velocity and changing velocity/acceleration from verbal description, label, or video
  • Analyze other rate problems (including the house painting problem)
Wiggins & McTighe say that assessments should be designed around problems, rather than around exercises. (A problem in this usage is like an actual soccer game, while an exercise is shooting drills or dribbling drills.) What problems are related to velocity? Last summer I started working on a problem revolving around an elementary school across a very busy street from a park. I was thinking about asking students to try argue for/against the need for a pedestrian bridge to allow elementary students to safely get to the park for recess/science class. Another possible problem might be train or bus scheduling: if I need to provide bus service along a certain route for a certain number of passengers, how many buses, leaving how often, moving at what average speed, etc. (And why do buses clump up, anyway?) I suppose network traffic and download speeds are an extension of that idea. (Dan Meyer's "Boat in a River" is probably at least as good an intro to velocity as the Modeling Physics two-buggy lab. But that's how to teach, not how to assess, and that's supposed to wait until later in the process.)

There's also the idea that assessment should provide a scrapbook, rather than a snapshot, of what students know. Having students assemble the scrapbook/portfolio also asks them to develop their self-knowledge/meta-cognition so that they can recognize good work when they see it. Teaching that is way harder than getting students to recite Newton's Laws...

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