Days 42 and 43: Careless mistakes with decimals; exponent reflection

We’re heading into decimals as integers. I want to make sure the students know place value so I gave the standard classes a pre-test on adding and subtracting positive decimals. Before the pre-test, I talked about attending to precision and I specifically asked the students to rewrite the problem vertically to avoid careless mistakes.

Students shared their work on the whiteboard and we talked about each problem.  Of course I had a few who did not take my suggestion to heart. I didn’t have my smartphone handy to capture the actual student work, but below is a recreation of a mistake one student made with the first problem.

decimal mistake

This was a great mistake because it generated a conversation about place value, but I was soooo disappointed the student didn’t rewrite the problem to solve. Perhaps the problem was too easy so they didn’t feel it was necessary to rewrite it. But what’s going to happen when they encounter decimals as integers.

decimals as integers

At the end of the period one of the students I had last year came up to me and said, “I’m not being challenged by this, Mrs. Dooms.”

I said, “I understand, Mark.” I walked over to the white board and showed him a problem like the one above. “I want to make sure you remember how to add decimals because next week we’ll be doing that.” He stared at the problem, grabbed the dry erase marker, took off the cap, but made no attempt.

“Ok. I’ll be challenged next week.”

Pre-algebra reflection

On Thursday, the pre-algebra students were assessed on the exponent rules they’ve learned thus far. It ended up taking longer than expected for some so they finished up on Friday. As students turned in their assessment they stapled practice the problems I assigned as optional homework. It led to an interesting exchange with one student who chose not to do it.

“You left some problems blank.”

“I know. I don’t know how to do them.”

“We’ve done them before and they’re just like the practice problems I gave to help you get ready for the test.”

“It was optional so I didn’t do them.”

At first I’m thinking this is a good lesson for him to learn. On the other hand where’s the hole in my teaching? Why didn’t I catch that? Looking back to when the original lessons unfolded, he was showing me he grasped the concepts during individual whiteboard work. We even spent the entire block reviewing for the test. I was a hawk catching mistakes when the students practiced in pairs with the “Around the World” activity. The next time I see him I’m going to ask if he pushed the Expo marker or did his rotating partners do the work.

I need to reintroduce exit slips.

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4 thoughts on “Days 42 and 43: Careless mistakes with decimals; exponent reflection

  1. Mary
    I just wrote a post about my current failure with exit slips. It dovetails nicely with this story about the Pre-Algebra student. I am absolutely at a loss as to how to solve this problem. My kids are in a different place than your Pre-Algebra student but they are each sending the same message – If you don’t grade it, it doesn’t count. My guys are doing this because they have convinced themselves that they are too busy and can only do what they HAVE to do. This leads them to slack off until about 18 hours before a test and then they frantically prepare for that assessment. This pattern repeats often enough so that they legitimately don’t have time for their daily work because they are consumed by a cycle of cramming for the next assessment. But – they are grade conscious to the point that they’ll do almost anything I ask them to do (sometimes dishonestly) if that thing is being graded. How have your exit slips helped with the problem you describe above? It’s entirely possible that I am just misusing this idea.

    • Hey Mr. Dardy,

      I’m thinking that perhaps this student fell through the cracks and I could have caught it with an exit slip. I do a lot of individual whiteboard work as a check for understanding. Maybe he was watching his neighbor solve the problems and he wasn’t thinking on his own. But he could have done the same thing on an exit slip. The “artifacts and data” are only useful if the student is doing his/her own work.

      I gave a week’s notice for this assessment and when I reassess the students are required to complete an evidence of study sheet in which they are required to practice 5 days out of seven and get a parent signature. In instances where the students cram would an evidence of study sheet–absent a parent signature–fly at your school?

      • Mary – Nice idea. The particular students I am thinking of are both resident students in the boys’ dorm where I live – so parent signatures are off the table anyway. I have a colleague who does announced HW notebook checks but what I see kids doing is just frantically cramming in the HW just before those checks. Sigh…

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