Prior to this lesson, my students designed their investigations in Planning Bio Bottles. Having a day in between gives me time to correct any student misconceptions and make sure they have a clear plan for assembling their Bio Bottles.
I pulled a few anonymous student samples with clear plans to share with the class, and then a few that needed significant revising. This provided models for success, and gave the corrective feedback in a more explicit way than any notes I wrote on papers would have done. Then I returned the plans, and had students glue them into their science notebooks.
Next I took them up to our science lab, where parent helpers had laid out materials and tools. I reminded students to use their plan, and help each other out when needed. The amount of time it took kids to finish varied greatly, so I had early finishers add predictions to their notebooks. For detailed information on how to actually build the Bio Bottles, go to Bottle Biology.
Because I tried to do the planning while they were building (see my reflection) you'll notice that what their variable was still very much up for debate.
The Bio Bottles are fairly low maintenance, so I really only need to take time for my students to collect data to answer their experimental question. Their outcomes are easy to measure, either the height of the plant, the height of the water, or counting levels and sprouts. After a couple of weeks, I'll let students take them home with parent permission. I don't think the bus drivers are going to allow those.