Things are getting better. This material seemed more familiar to the students, so there was less fight about whichever method I used.
I used the traditional modeling approach to the discussion in 2nd hour and it went OK. It didn't blow the doors off the room or anything, but we got through most of the worksheet, kids were generally respectful and there were some solid questions asked. One of the presenting groups asked if they could purposely put a mistake in their board to see if the class would catch it. That was pretty cool.
Both for time and behavioral concerns, I took more control over 5th hour. I still had groups whiteboard problems, but instead of turning them loose to carry on a class discussion, I walked around the room myself and stopped to interpret what I saw on each board. This took the load off students who may be afraid to present and it also gave students a chance to see how I think. I made a point to emphasize that I was still not giving out correct answers, I was simply acting as a medium between the presenters and the class. That seemed to be a compromise they would accept.
Tomorrow is the quiz on solving systems both graphically and algebraically. I don't emphasize elimination as a method because I feel that if you give students with a shaky foundation too many choices, they'll start mixing and matching pieces of each approach. KISS - if you can graph it, do that. If not, use the magic of algebra.
The major thing that's struck me through this unit is that regardless of how familiar the students are with this content they've all seen before, they have no idea what they're really doing. What I mean is that they might be able to follow the steps needed to calculate slope, but they have no real concept of what slope is and why it's relevant. I think I've already noted this here, but it popped up again with solving lines graphically. "Where's the solution?" "it's right there (pointing)." They could graph the lines OK, but too many struggled with a) knowing what a solution is and 2) correctly identifying the coordinates of a point from a graph. How can students graph lines and not be able to label the coordinates of a point?