Mail Time: Avoiding extensive homework review in class

Posted homework solutions
are like nuclear weapons...

Lisa Zavieh, an "acorn"* at the 2011 AP Physics reading, writes in:


* An "acorn" is a first-year AP reader, so called because her nametag includes a sketch of an acorn in the corner.  A "grasshopper" is a first-year AP table leader, so called because someone thought it sounded cool.

"One thing I have been mulling over for awhile is how to handle homework. I completely agree with grading homework, and with assigning minimal amounts daily with the expectation that students will present thoughtful thorough solutions.  I also do not accept late work, and like your extensions and exemptions policies.

I would like to avoid copious HW review during class, so my response has been to post homework solutions (in the past - on paper. Now I am considering video clips.)  What do you do in your class?"

It's great to hear from Lisa. The AP reading is an amazing source of teaching ideas. I'd say that 2/3 or more of what I do in my class is inspired by a conversation from the reading. Lisa's "video clips" thought is likely based on a brief presentation by Misissippian Marsha Hobbs, who showed us some wonderful videos of her doing physics problems. If I were taking a class online without daily personal contact with classmates, I would want access to a set of Marsha's videos.

But Lisa, to address your specific question, I think I recognize the in-class conversation you’re trying to avoid: “How do you do problem 2 in detail?” say the class. If you don’t go through every last little step of problem 2, it becomes “Mr. Jacobs is so mean and unfair. He won’t even show us how to do the homework. How are we supposed to learn physics if he won’t help us find our mistakes?”

For about the first seven years I taught, I posted homework solutions. I was able to tell the class, “If you have any specific questions about the problems, the solutions are posted. Take a look after class. But for now, let’s figure out how to do *tonight’s* problems…” That didn’t completely prevent the whining at first, but it allowed me to checkmate such a complaint. “My daughter says you didn’t go over the homework. How is she supposed to learn?” “Oh, she never came to talk to me, so I figured that she had compared her work with the posted solutions, and didn’t have any further questions. Did she study with the posted solutions?”

In practice, very few students ever looked at my solutions. And if they did look, they checked the answer and moved on. No matter how beautifully I modeled the problem presentation process, no matter the clear verbal explanations I included, a student didn’t care. Right answer? Great, move on. Wrong answer? Dang, move on.

Posted solutions were like nuclear weapons – they were for having, not for using. After a few years at the same school, parents and colleagues no longer questioned my competence, so I didn’t need the CYA aspect of posted solutions; and I had become good enough at problem solving that I didn’t need to write out every step of every assigned problem for my own sake. I saved a lot of time by not writing out solutions anymore. (I now have available a set of Giancoli 5th edition solutions in a couple of three-ring binders – bidding starts at one case of canned Skyline Chili.)

So how do I now preclude the calls to go over homework in detail? I *want* to discuss important physics issues about the problems, but I don’t want to do a problem step-by-step. Thing is, I know what the major sticking points will be on most problems. One of my daily quiz questions might refer to an issue on a homework problem: “Which of the following is a correct free body diagram for problem #2 last night?” By going over the quiz, I’m also going over the homework. I rarely ask, “any homework questions?” Rather, I ask the questions myself: “You weren’t given the mass of the roller coaster, so how did you solve the problem without that information?”

I make sure discussion is on *my* terms. This means questions about physics concepts are fine, but questions about how much credit they might get for their answer are unacceptable. If a student presses his questions beyond the scope I want to deal with during class, I politely offer to continue the conversation during the daily consultation period. Somehow, though I’m sincere in my offer, that student rarely ever shows up on his own time to talk physics with me. Go figure.  :-)

GCJ