Although terminology is used for clarification, it can also be a hindrance to embracing new ideas. The terms algorithm and computational thinking are not new and donāt have to represent difficult concepts, but used in connection with young pupils for the first time they may cause some anxiety.
The purpose of this chapter is to demystify these terms and consider how we can meet the National Curriculum Programme of Study requirement for pupils in Key Stage 1 (KS1) to understand what algorithms are and how they are implemented on digital devices; and that programs execute by following precise and unambiguous instructions (DfE, 2013). The focus is on meeting the statutory requirement in a manner which professionals would consider manageable, appropriate for the age range and embedded in good practice. This can be achieved without the need for āexpertā knowledge and even in many cases without the need to use a computer!
Computational thinking should be seen as a problem-solving process, which incorporates the use of algorithms by analysing and logically organising data.
This lesson focus is on algorithms being a sequence of precise instructions and related to the need for digital devices also to have precise instructions, in order to follow a preset program with a predetermined outcome.
Be clear in your own mind what an algorithm is and how the concept can be embedded in a cross-curricular way.
Pupils need to be grouped according to ability.
After an initial teacher demonstration, this particular lesson plan focuses on creating an algorithm for cleaning teeth, which would link well to personal, social, health and economic education, and with a topic on āAll About Meā. The principle of this lesson could also be used in many different contexts, for example, crossing a road, making a sandwich, getting dressed.
Lesson outline
In order for pupils to understand the term āalgorithmā, they need to create some of their own and try them out in the physical sense. This all takes place away from a computer but is related back to digital devices.
Class introduction
The pupils are told that today their teacher is a robot and needs to be programmed to make some toast. Can the class help?
The teacher needs to follow the exact instructions the pupils give. It is important to be pedantic and petty. Relate this to the need for any digital device to have precise instructions. Throughout the lesson be aware of the language you use: the term algorithm is very likely to be new to them but they may also need help understanding words such as precise and clear. It is important not to make assumptions about pupilsā understanding of language.
Commentary
Model the instructions using the toaster and write the final solution to make one slice of toast on the interactive whiteboard. A piece of toast as a reward for a group with great ideas may be well received!
One possible solution is presented below:
1. Open the packet of bread.
2. Take one slice of bread out with your hand.
3. Put the bread in the toaster.
4. Push the lever on the toaster down.
5. Wait until the toast pops up.
6. Take the toast out of the toaster with your hand.
7. Get a plate.
8. With your hand, put the toast on the plate.
9. Get a knife and margarine.
10. With one hand holding the tub of margarine, use the other to take the lid off the margarine.
11. Put the knife into the margarine and put some margarine on it.
12. Hold the plate with your left hand.
13. With the knife in your right hand, spread the margarine on the toast.
14. Put the lid on the margarine.
15. Pick the toast up in your hand.
16. Eat the toast.
17. End.
The sequence above is not the only answer, but whatever solution the pupils decide should be modelled on the interactive whiteboard. It is possible to be even more precise than the above solution. The algorithm could be decomposed into a whole series of further steps (for example, about the process of eating), but we need to assume that the human robot has some such functions already programmed into its memory.
Commentary
A development would be to ask pupils to make a decision as to whether they would like more than one slice of toast. This would involve an alternative loop, with the last four steps being:
Eat the toast > Repeat until no longer hungry for toast > If no longer hungry for toast > End
Classroom organisation
Put the pupils into ability groups of three or four. They are to use all or a selection of the cards drawn up from the list below, depending on their ability. The most able are given a selection of cards and have to work the rest of the algorithmic sequence out. The middle-ability group are given all the cards to place in order. The less able pupils will either have adult support or be given enough cards to create the algorithm, which wonāt have been decomposed into as many steps.
When the cards are considered a working algorithm, the pupils should Blu-tack them to a surface.
Further differentiation might involve having bogus cards in the pack or asking the most able to complete the task without using the word ābrushā!
The following will be cut up into each step and laminated.
Algorithm for cleaning teeth (a possible solution)
ā¢ Pick up the toothbrush with your hand.
ā¢ Turn on the tap with your other hand.
ā¢ Rinse toothbrush under the tap.
ā¢ Turn off tap with your hand.
ā¢ Pick up the toothpaste tube with your hand.
ā¢ Hold the toothpaste and toothbrush in one hand.
ā¢ Unscrew toothpaste top with the other.
ā¢ Squeeze toothpaste tube.
ā¢ Squirt the toothpaste on to the brush.
ā¢ Put the toothpaste down.
ā¢ Open your mouth.
ā¢ Brush your teeth for two minutes.
ā¢ Spit into the washbasin.
ā¢ Close your mouth.
ā¢ Turn the tap on with one hand.
ā¢ Hold the toothbrush in the other hand.
ā¢ Rinse toothbrush.
ā¢ Turn the tap off.
ā¢ Put down toothbrush.
ā¢ Hold the toothpaste tube in one hand.
ā¢ Screw the top on with the other hand.
ā¢ Stop.
Peer assessment
Pupils share their algorithms with another group and they assess whether the algorithm would work.
For evidence of the pupilsā work and for follow-up activities, it would be valuable to take a digital photograph of their completed algorithm. This could be uploaded to an e-journal or kept as a hard copy.
Commentary
It is important here to tell the pupils that they are considering whether the sequence actually works. Although an algorithm needs to be precise, there are many ways to complete it.
Mini-plenary
This would be an ideal opportunity to celebrate the pupilsā work and discuss the solutions they have found.
The next stage of the lesson would be to introduce the idea of debugging a program. This would involve each group changing the order of four of the steps (decomposition) in the sequence and another group would need to correct (debug) the revised sequence.
Commentary
Endeavour to use the correct computational language here, for example, debug the sequence rather than correct the errors.
The teacher should ask the pupils to suggest anything in their home they think would have an algorithm to enable it to work. Examples here would be a washing machine, dishwasher, television remote control. If possible, show a simulation of a washing machine following an algorithmic process.
Plenary
The lesson ends with self-assessment. The use of mini-whiteboards may be of value here.
Rather than asking vaguely āDo you understand todayās lesson?ā, be more specific, such as:
1. Write or draw an example of a digital device that uses an algorithm.
2. If you are asked to debug something, what does that mean?
3. What happens if an algorithm is not clear and precise?
The self-assessment questions should relate back to the learning ob...