Using Adam Boxer's simplified model of cognitive load, we can make some simple conclusions:
Students who lack knowledge of the relevant science during the lab don't learn as much because they have fewer resources (i.e. fewer resources leads to higher cognitive load which in turn leads to reduced learning). For this reason, discovery labs rarely work.
Lab equipment can be a source of additional cognitive load if students don't have sufficient experience with the tools.
Using intergraded instructions in labs (a.k.a. visual practicals) are a way of scaffolding by providing students with external resources that lower cognitive load.
What follows is an exposition of ideas for the teaching of the practical component and for its evaluation.
Teaching The Practical Component
Introducing "slow practicals". These are a set of routines to do before and during the lab that lower cognitive load (hence make learning science easier) by reducing the task demand as well as by increasing internal and external resources. Like any routine, it needs to be explicitly taught and practiced frequently so that labs run smoothly.
Increasing Internal resources
In general, students entering the lab need to already know the skills and concepts they will be applying and looking for respectively (i.e. students should not be building the plane while flying it). If teachers choose to do an inquiry (or discovery-style) lab, they should know that this tends to greatly increase cognitive load, therefore students may need more external resources to help compensate or, teachers ought to be confident their students are capable and ready for the challenge.
To increase internal resources, consider pre-teaching key things students will need before entering the lab. For example, allow 15-20 minutes at the end of a class to manipulate new lab equipment so that the equipment itself is not an obstacle to the learning on the day of the lab. If simulations for the concept being taught exist, allow the class to explore them before the real experiment (e.g. PhET and JavaLab).
an interesting approach to labs (or teacher-lead demos) is P.E.O.E. which stands for Predict-Explain-Observe-explain.
Increase external resources
Another way of reducing cognitive load is by providing scaffolds (external resources). An interesting approach to this is a technique called "Integrated instructions" or "visual practicals." Click here for examples.
Scaffolds are meant to be temporary. Help students become independent of them by fading them slowly. Perhaps have students practice turning the visual steps into written procedures.
Read more about this here on David Paterson's blog.
What makes the practical "slow?"
A useful strategy to manage cognitive load is to break up more complex skills into smaller manageable segments. We can do this in our labs with the following routine:
Gather students at teacher's demo table.
Demonstrate and explain one segment of the lab (one step in the procedure).
Send students to their stations to copy what they saw teacher do. Perhaps they are also tasked with thinking about or observing something while at their stations.
When students have finished, gather them at teacher's demo table again and repeat steps 1 through 4 until the lab is done.
Here are some advantages this may have:
reduced cognitive load (leads to more learning)
teacher can ask probing questions at demo table
teacher does not need to repeat themselves to 15 groups (i.e. say it once at the demo table)
chance for error is reduced because students have just observed their teacher.
A disadvantage, of course, is that labs are slower.
Evaluating the practical component
Clearly, we are required to respect the MEQ's Framework for Evaluation.
That said, reducing extraneous cognitive load during exams/evaluations allows students to apply more of their working memory to problem solving.
Grading is the teacher's prerogative. Perhaps departments ought to come together to co-create marking schemes or rubrics for homogeneity and rigor.
Two-stage exams are evaluations that happen in two parts. Typically there is an individual portion and a collaborative part. The weight of each is up to the teacher, but usually the individual portion weighs more.
Do "mock" Lab Exams for the purpose of giving feedback on how to do lab exams well. Take the opportunity to show students high and low quality lab exams from previous years so students see quality.
Give students the marking scheme/rubric to study before the lab exam. have a conversation about the levels of quality in the rubric - students and teachers don't understand the descriptors in the same way.