First the struggles. I've seen students seeking "right" answers. Students grow accustomed to a model where the teacher provides knowledge and students memorize it. Then they follow that up with a regurgitation of the knowledge, providing correct answers. This process doesn't work with the NGSS, as students are expected to reason and create their own understanding. This difference was highlighted before our most recent assessment. Students knew that they were going to have to create a model showing everything we'd learned about photosynthesis. We had brainstormed the criteria for a complete model (based on our understanding). Students trained on the knowledge regurgitation model asked, "Can you just give us a model to study from?" While this would have ensured that students' models contained all of the necessary information, it would have reduced the cognitive load for them. Instead of having to assemble the pieces into a coherent model, all they would have to do was memorize and replicate my model. Needless to say, I did not provide them with a sample model to study.
Now for some success. The results of this particular assessment helped me to see that students were in different stages of concept attainment. Some students had a thorough understanding of what happened in the chloroplasts (minus the biochemistry, per the standards) and knew how each piece of the equation entered or left the chloroplast, leaf, and the tree. Other students had an understanding of the process, but they had not yet made the connection between the subsystems that make photosynthesis possible (e.g. xylem/phloem, leaves, and roots) and the chloroplast. Still other students had somehow evaded their responsibility for building their own understanding, providing me with a "model" showing a tree releasing oxygen while taking in carbon dioxide.
So, now it's time to regroup and figure out how to help the students who didn't get it, move from that to "got it." I'm not sure how exactly to do that, but I'm thinking of having them trace one of the reactants or products of photosynthesis on it's journey through the tree, to or from the chloroplast.
Stay tuned for more updates as we press on, helping students move from vessels to contain knowledge to active participants in constructing their own understanding using the same kind of practices that scientists do.