Modeling Bad Behavior

A couple days ago I was using an aluminum foil boat to collect data for our math class. We were practicing on mean, median, mode etc. (see post below) and I wanted to tie it in to what I had planned to do in science. As I conducted the experiment the students kept asking me about what I was doing. They knew it was to collect data, but they wanted more information. Kids get indignant when you refuse to share information with them!

A thought occurred to me and I decided that perhaps it would be a good idea to have them watch me do an experiment and allow them to critique what I did. This would give me a good idea about what they already know and what we should focus on. Today I conducted the experiment.

I was looking for the students to identify a few specific behaviors that I modeled incorrectly including:

1. I did not have my instructions for the experiment.
2. I did not do any measuring or data collection.
3. I played around by shaking the wet aluminum boat at a nearby student.

Most of them didn't identify any of these three behaviors. They were more focused on safety (I didn't wear gloves!) and the fact that I left my tools out instead of putting them away. I suspect that both of these ideas have been well instilled in them and now I know where to put in my effort.

Was this a better pre-assessment than giving them a multiple choice test?