The impossible bridge
- Remind students that the main idea is what the author wants readers to understand is important and valued in the text as a whole.
- You may wish to explain to students that finding the main idea is hard, but that it can be found if they first work out which information is important to the text, i.e., the whole text. You may also wish to explain that important information will be mentioned more than unimportant information.
- Explain to students that a) assesses if they understand which information in "The Impossible Bridge" is important. Tell the students that first they need to read "The Impossible Bridge", then tick two boxes next to the information they think is important.
- Explain to students that b) assesses if they understand what the main idea is. Tell the students they need to think about the important information they identified at a), then put a tick next to the main idea.
- Consider how the text and the task should be presented to your students, to support effective comprehension of the text and completion of the task. This might involve independent reading by students, presenting the text and task as a shared or guided activity, or using a combination of these approaches.
- Responses can be discussed by the teacher and a student only, or within larger groups.
- use comprehension strategies
| a) |
The two pieces of important information are:
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| b) |
The main idea of this text is:
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Knowing the difference between plot and main idea – About a quarter of the trial students incorrectly thought the main idea was the same as narrative plot.
In discussions with the researcher, these students revealed they thought some of the vocabulary prevented them from understanding the text. They clearly had some understanding that there was a problem with their comprehension, and also that it may have been caused by some of the technical vocabulary. However they did not have the strategies to fix the problem. These students neglected to use the photographs to help them work out the meanings of words like "beam", "arch" and "truss". They also neglected written information such as "You can join triangles together to make a 'truss'. A truss can make a bridge really strong." (p.10.)The word "suspension" also posed problems (i.e., its meaning – this resource is not concerned with whether or not students could decode the word). "Suspension" is an example of nominalisation – a process by which verbs, and sometimes adjectives, become nouns. For example, instead of using verbs to describe a bridge where "cables are suspended or hung from towers", the bridge is described using a noun – "suspension". Nominalisation is often problematic for students because children's speech uses mostly verbs. It is usually only at the upper primary level that they are able to begin to replace verbs with nouns. Nominalisation causes a particular problem in this text because the meaning of "suspension" is not explained using language that is familiar to children – verbs.
Discriminating between important and minor details – Only about half of the trial students correctly identified both pieces of important information, 'Strong bridges can be made from card', and 'Different shaped bridges can be made from card'.
In discussions with students who did not choose either or both of the correct options, it was revealed they had based their choices on personal interest. They had not found the correct options interesting, so believed them to be unimportant. They did not seem aware that these options were important because details relating to both could be found right through the text.
About half the trial students incorrectly chose 'A truss can make a bridge really strong' as important information. From discussions with the researcher, it appears they chose it because they found the concept of a truss interesting; some also found the sound of the word interesting. They were not aware that because details about trusses were only mentioned on three pages, and were not mentioned at various intervals throughout the text, they could not be said to be important enough to help find the main idea.
Finding the main idea – Nearly three quarters of the students chose the correct main idea, 'Several types of strong bridges an be made from card'.
This may seem unlikely given that only about half the trial students correctly identified both pieces of important information. However, this result has been reasonably common across the trials of main idea resources. It may occur because students simply have to choose between three options of main idea, and this makes b) achievable even for those who cannot find the main idea independently.
This particular task also provides considerable scaffolding for the students in that the phrase 'can be made from card' is used in both pieces of important information in a) and is also used in the correct main idea. This was done as a means of scaffolding students towards understanding that important information will be represented in the main idea.
Students who have some understanding of narrative plot but none of the concept of a text having a main idea are likely to confuse the two when first introduced to the main idea comprehension strategy. Begin to introduce the concept of main idea through shared reading. For example, introduce Cinderella by telling your students its main idea is that goodness and beauty will always triumph/come out on top over nastiness and ugliness. Throughout the reading, stop at various points to ask your students if they have noticed any details about goodness and beauty or nastiness and ugliness. Make two sets of these details on the whiteboard as you read. Once the reading is finished, support your students to think about the happy ending of the story, and how the ending and the two sets of details might be combined to make the main idea.
Brainstorm other familiar narratives with your students. Discuss what the possible main ideas of these might be as distinct from the plot, or storyline.
Students who struggled with technical vocabulary:
This group of students were sufficiently skilled at self-assessment to know they had a comprehension problem, and to have formed ideas about what might have caused the problem, i.e., technical vocabulary. These students now need to be supported to make use of the context when faced with unfamiliar vocabulary. Most of the technical vocabulary in this text is explained by the context – through photographs and/or text, e.g., there are photos of trusses on pages 8 and 9, with text explaining them on page 10, i.e., "You can join triangles together to make a ‘truss’. A truss can make a bridge really strong." Support these students to make use of contextual clues by discussing the two different types of clues, i.e., the photographs and the written text. First look at the photograph of the beam bridge on page 3, and explicitly link it to beams in buildings or a beam used in gymnastics (draw them if necessary). Discuss what beams look like and what function they have. Ask the students how they can use what they know about them to work out what a beam bridge is. Work through the same process with the arch bridge, but this time expect them to work more independently. Finally, focus attention on the written clues about trusses on pages 8 and 10, as well as the photograph on page 9. Ask the students to link the two types of clue in order to explain what a truss looks like and what its function is. Expect these students to be able to pinpoint exactly which evidence they use to do this. Finish by asking them to think of examples of trusses around them.
The nominalisation "suspension", however, is not sufficiently supported by contextual clues even though there are several photographs. Support your students to explicitly unpack the meanings of nominalisations by using verbs. In the right hand column below, the verbs are italicised:
| Hard word | What does it mean? |
| Suspension | When something is suspended or hanging down |
| Evaporation [not in this text] | When a liquid evaporates or becomes a gas |
| Condensation [not in this text] | When a gas becomes a liquid |
| Development [not in this text] | When someone or something develops or changes in some way |
| Behaviour [not in this text] | The way someone or something behaves or acts |
| Rate [not in this text] | How quickly or slowly something happens |
Students who struggled to discriminate between main and minor details:
Use this template with students to find details in the text about the same ideas that were presented in a):
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Strong bridges can be made from card:
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Emma used the internet:
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A truss can make a bridge really strong:
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The first bridge bent in the middle:
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The suspension bridge was awesome:
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Different shaped bridges can be made from card:
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Students who struggled to find the main idea:
Ask your students to look for details relating to:
- Strong bridges can be made from card.
- Different shaped bridges can be made from card.
Encourage a discussion about how these two groups might be combined to find the main idea. Prompts might include: "We can see that there are a lot of details about making strong bridges out of card, and also a lot of details about the different types of bridge that can be made from card. What might we say about these things together? How might we combine these two groups of details? Which main idea tells about both groups together?"
For Ready to Read teacher support materials for this text, go to: The Impossible Bridge / Ready to Read Colour Wheel / Instructional Series / English - ESOL - Literacy Online website - Instructional Series (tki.org.nz)
What's the main idea? Research and articles | Assessment Resource Banks (nzcer.org.nz)
Duffy, G. (2003). Explaining reading: A resource for teaching concepts, skills, and strategies. NewYork, NY: The Guilford Press.Ministry of Education. (2003). Effective Literacy Practice in Years 1 to 4. Wellington: Learning Media Limited.