Before addressing this display, students/class should have collected their individual body weights as well as their backpacks' weights (packed up as if they had just arrived at class).
To ensure student participation, ensure no names are tied to the individual points (some students may be sensitive about their weight being displayed publicly). Tilting the scale display away from onlookers, collecting data in the hallway outside the classroom, or entering numbers in a list on a calculator are all effective ways of ensuring students' weight can be collected and shared in a discreet manner.
For other guidance and tips, please see my blog post about this lesson at:
[url]http://scottkeltner.weebly.com/1/post/2012/10/linear-inequalities-lesson-pack-up.html[/url]
