A practical question

Before I launch into this week’s burble, I had a lovely e-mail from Liz, asking if I knew the Tom Lehrer Elements song. Indeed, I do! And my Year 7s also introduced me to another version of the same thing which you’ll find yourself singing in the bath. As for the Tom Lehrer classic, get your class to learn it and then sing along to this Powerpoint where the Elements appear in the order mentioned…The Periodic Table for song only

So last week I burbled on the value of writing your own test papers and questions. I signed off with a mention of the practical questions that I put into the Year 7 and 8 summer exams.

Before looking at them in a bit more detail, here’s why I think you should include some form of practical assessment in end of year exams.

  1. It’s a fundamental scientific skill – of course we should be assessing it!
  2. It makes them take the practical stuff a bit more seriously – yes, it’s fun and motivating, but you also need to be good at it if it’s to have value
  3. It makes the exam a bit different to all their other exams. I try to get them to think of tests/exams as a Fun Frolic rather than a Terrifying Test, and including a practical question really helps with this.
  4. It allows students who have excellent practical skills but are maybe not so strong on the theory to feel good about science

There must be other reasons. If I think of them I’ll add them as I go along.

So, Year 7s. Huge emphasis on practical work throughout the year. Absurd not to include something in the exam. What could we get them to do? Inevitably, when the entire year group is carrying out an activity – rather than just one class – the practicality of your practical is important – always think of your technician! So I decided against a wet experiment or a burning investigation. Some kind of microscopy exercise would be easy to set up, easy to clear up, easy to mark, and, again, would focus (sorry…) attention on this as an important skill that’s worth getting right.

Their introduction to cells involved actually looking at cork and onion cells, and they built their own model plant cells. So my wonderful technician sourced some old stem TS slides, blocked out the original labels, and we were good to go. The logistics of the exam meant that two girls had to share one microscope – so one did this question first, the other did it later. Not a problem.

Now then, the interesting bit. What did I want the exercise to cover?

OK, first bit, could they actually use the microscope? You know, turn it on, put the slide in the right place, focus on the tissue accurately. See something…. I tried to keep it simple.

Observe the slide under low and medium power (to keep them away from the fiddly fine focus of HP). If they managed to do this without assistance, they gained one mark (but they were instructed to ask for help if they couldn’t focus the microscope – as they would lose the skilful mark, but gain access to all the other marks).

Draw one cell. Three marks.

Here I wanted to see if they understood what a cell was when looking at lots of them. So a drawing of a single cell, regardless of the quality of the drawing, gained one mark. Lots of them drew hundreds of cells. Never mind – did their drawing resemble the specimen? If it did, then lovely drawings of lots of cells gained the next mark. Deranged scribbles of one cell did not.

The final mark was a general one for quality of drawing. Did they use a pencil and fill the space? Was it drawn not sketched? Did it have nice clean lines and no shading? If so, the final mark. Next year, I think I’ll award two marks for the quality of drawing to really reward the careful, patient, observations.

Finally, could they interpret what they could see?

Do you think your drawing shows an animal cell or a plant cell? Explain your answer. Two marks.

Plant cell got them one mark. I hoped they would pick out the cell walls and/or infer the large vacuoles for the second. “Plant cells – because they’re not moving around” only gained one mark.

Did the question achieve what I wanted? Well, they certainly took it very seriously. There were lots of quite beautiful drawings and fewer total disasters than you might expect. The mark allocation differentiated nicely and staff reported it as easy to mark.

The Year 8 practical exam questions was more challenging. And I’ll talk about that next week….or rather, the week after, as half term is upon us! I’ll be camping with my family on the Isles of Scilly. Hope you have a good one.

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