Observing practical science
Teaching great practical lessons is one of the great challenges of teaching in the sciences. There are so many aspects to balance as a teacher in terms of lab management, unexpected student questions, learning skills vs learning content, risk, time efficiency, etc. And the list goes on.
So, as an observer, what tells me when the practical lesson I am watching is great (or maybe more helpfully, what are the signs it's not so great)?
1. Students can contextualise the practical
When practicals are really working, is when students know what the practical is about, how it works, what they are learning from it, and how it fits in with the theory they already know. The easiest way to do this is by adding a few pre-lab questions at the start, before students get on with their practical, so that the teacher can cross-examine the students' understanding of the context before they get started. Another method is to set the practical up as a conflict (something I have written about on my blog here, and for Education in Chemistry here).
It's very easy to pick up as an observer if the students don't get the context. Students cannot make modifications if something doesn't work, or proceed if the instructions are unclear, if they don't feel they have a grasp of the underlying sciences. When questioned about the practical, students will give very one-dimensional answers about the practical:
Observer: What are you measuring here?
Student: Uhh [checks circuit], the current.
Whereas a student who grasped the context could give a much more developed answer:
Student: I am recording the current so that I can see what kind of relationship there is between the voltage and the current. Then I can work out whether or not it fits with the equation that we have learned, and even work out the resistance of the circuit.
2. The teacher is not repeating themselves over and over again
One of the real dangers with practical work is that students pair off, or work on their own, and the whole-class instruction giving is over. Teachers I have observed often spend a lot of time moving around the room giving the same follow up instructions to each pair, rather than asking students to think. This makes the teacher a much less valuable resource in the lab than they should be as the expert full of deep knowledge; they become an soundbite for the students.
The three best ways to tackle this are:
When asked a question more than once, teachers getting the attention of the whole class to give the extra bit of information, and then questioning to check students have picked up the instruction, before letting them get back to their practical.
Or, another approach is to ask the pair you have just explained it to, to pass on their new knowledge to the next pair. This reinforces learning for the first pair, and ensures the teacher is focusing on assessing students progress and understanding of the science, not just the comprehension of instruction.
Ensuring that tasks are set up in a sufficiently clear way at the start. And checking that students have understood the instructions. After a lesson with lots of repetition of the same questions, the teacher needs to go back to the drawing board and redesign the resource sheet to give them the right structure and clarity. It's great if students have some open-endedness in the task design, but what this might look like, and in which aspects, need careful communication.
3. Students are thinking throughout
When I am observing, I am constantly asking myself about what students are thinking. And they should be thinking all the time. One of the big give-aways for poor practical work, is that students are thinking when the teacher is talking to their pair, but the rest of the time they are not. They are chattering about something else, staring out of the window, playing with bottles of distilled water, and suchlike.
There are two main reasons why students might not be thinking during experimental work: either the cognitive load is too low, and students need to be given more opportunities for deeper thinking during the task; or the cognitive load is too high, and the teacher needs to scaffold the learning better.
There are lots of ways to achieve a balanced cognitive load as a teacher, and here are a few ideas:
Have questions next to each step of the method for students to fill in about what they are observing, why something is happening, the risks, potential sources of error, etc. They should do this as they are working through the practical. These are generally the questions teachers ask as they move around the lab, but this ensures that all students are thinking about them, not just the pairs the teacher is spending time with.
Ensuring a balance between different kinds of task within the practical. This might be between the dextrous skill of setting up an organic practical, and also some more analytic work on the products, or having some preliminary testing followed by an open-ended investigation using the results (this is great for picking up CPAC skills at A-level). The switch in task leads to a switch in thinking which keeps the pace up.
Having the minimum number of repeats of a task required for students to get the kind of results you need for the learning. Endless repeats mean students are doing the same thinking endless times. They are not writing research papers, so the reliability and accuracy of their results is not as important as we often assume it to be.
Focusing the learning on either content acquisition or experimental skills at any given moment. So if the students need to learn both, then having one aspect heavily scaffolded, or leaving it for discussion after students have mastered the primary learning objective improves the flow of the practical significantly, as students are not floundering from the outset.
4. Students have ideas about how they produced anomalous results
When students really 'get' the practical work, they have a much better grasp of what's going on when they face the unexpected. As an observer, I often ask students about their data and I can really build up a picture of their learning from their answers.
In my experiences, great teachers link errors in procedure, to the actual effect on the data. Will this error increase or decrease the measured rate of reaction? Why? This means that students build up the skills to do this themselves, which is a really crucial aspect of being a scientist; knowing which data to keep, and which to cast aside.
I observed a lesson recently in which a student was plotting a graph of Ohm's law, and had an 'anomalous' point at a low voltage, which he had ignored for his graph plotting, as taught by the specification.
Observer: What kinds of errors might have caused this point to be anomalous?
Student: I think the temperature may have had an effect, as the wire was getting hot.
Observer: Good idea. How might you improve the experiment?
Student: I could have let the resistor cool between each experiment.
Observer: So which of your results on your results was taken when the wire was cool?
[Student points to 'anomalous' result]
Observer: So should we ignore that point for the graph?
Student: I suppose not, maybe I should actually ignore these points even though they look like a straight line.
This dialogue demonstrates that by asking students about error and making it a part of class discussion, the teacher can probe deeply into students' understanding of the content, but also their understanding of the procedures of science.
5. Students have ideas about how to manage risk
This final one is very similar and self-explanatory. Not only does this partial transfer of responsibility from teacher to student help make the learning environment safer and more pleasant, it also helps students' understanding of the underlying science. They can discuss the risks, and how to minimise them in a discussion with an observer, and often explain why they are problematic from a scientific as well as a health and safety perspective. And now students writing risk assessments is part of the CPAC requirements at A-level so students need to become accustomed to doing this, and the observer can actually see whether or not this is part of standard lab practice from the students' attitudes.
In lessons I observe where students do not have ownership over the risks, they do not behave as expected in a laboratory. And it's not really (entirely) their fault: they just have no understanding of why not to. As an observer, I would generally take this as a sign that the teacher did not really understand the risks either, which reflects poorly on subject knowledge.
Students need to understand risk themselves and behave appropriately in a lab; not just because of the risk, but also because it derails the very carefully balanced learning and thinking taking place in the eminently distracting laboratory environment.