If you’ve been following recent posts featuring the work of Dr. Jill Swale you’ll have 
come across her “Thinking Hats” activity that’s partly designed to structure classroom discussions.
If you want an activity that eases your students gently into the whole “6 Hats” process, “Plus, Minus, Interesting” is a simple evaluation exercise that uses the Yellow (advantages), Black (disadvantages) and Green (creativity) hats to evaluate a specific question or situation.
In the supplied example there are a range of Crime and Deviance “What If?” questions – from “What if drinking alcohol become illegal in Britain” to “What if there was Saturday prison for children not working hard enough at school?”.
If you want to use your own questions I’ve added a document with a selection of different types of evaluation table, although each is based around the “Plus, Minus, Interesting” format. There’s also no reason why you couldn’t use a grid drawn on a Whiteboard if you’re doing this as a whole class exercise.