this conclusions rubric from science buddies is awesome. I'm always stumped when it comes time to write conclusions, whether it's a lab report or a more general essay. This really helps get me started.
if you don't remember: what I'm doing is NOT asking my students to write up an entire lab report for every experiment that we do. In each chapter, I'm focusing on a different lab skill and just grading their work on that part of the lab experience. this chapter's lab skill is making conclusions.
I kept the experiment really very simple: burn cotton in a flask with a stopper on it. Easy enough to get a good result, but still enough chance for error that students can analyze and suggest ways to reduce that error (finding a way to get the stopper on faster). Their hypothesis is very simple too: does conservation of mass hold for this reaction?
The conclusions I've read so far are some of the best I've seen. In the past when students did a lab report, the conclusion was the most slapdash part of it, hastily thrown together so they can turn in their full report by the deadline. When they applied the rubric above, their conclusion paragraphs were really thorough summaries followed by a thoughtful application of the law of mass conservation.
Now I only hope that in January when they choose their projects for a full report, they remember how easy this conclusion was to write!